Erhalten Sie Zugang zu diesem und mehr als 300000 Büchern ab EUR 5,99 monatlich.
- Herausgeber: Crown House Publishing
- Kategorie: Bildung
- Sprache: Englisch
- Veröffentlichungsjahr: 2019
Peter Mattock's Visible Maths: Using representations and structure to enhance mathematics teaching in schools supports teachers in their use of concrete and pictorial representations to illustrate key mathematical ideas and operations. Viewing the maths lesson as an opportunity for pupils to develop a deep understanding of mathematical concepts and relationships, rather than simply to follow fixed processes that lead to 'the answer', is increasingly recognised as the pinnacle of best practice in maths education. In this book, Peter Mattock builds on this approach and explores in colourful detail a variety of visual tools and techniques that can be used in the classroom to deepen pupils' understanding of mathematical operations. Covering vectors, number lines, algebra tiles, ordered-pair graphs and many other representations, Visible Maths equips teachers with the confidence and practical know-how to take their pupils' learning to the next level. The book looks at the strengths, and flaws, of each representation so that both primary and secondary school teachers of maths can make informed judgements about which representations will benefit their pupils. The exploration begins at the very basics of number and operation, and extends all the way through to how the representations apply to algebraic expressions and manipulations. As well as sharing his expert knowledge on the subject, Peter draws on relevant research and his own experience of using the representations in order to support teachers in understanding how these representations can be implemented effectively. Visible Maths also includes a glossary covering the key mathematical terms, as well as a chapter dedicated to answering some of the questions that may arise from the reading of the book. Furthermore, the accompanying diagrams and models are displayed in full colour to illustrate the conceptual takeaways and teaching techniques discussed. Suitable for teachers of maths in primary and secondary school settings.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 300
Das E-Book (TTS) können Sie hören im Abo „Legimi Premium” in Legimi-Apps auf:
Ähnliche
Acknowledgements
This book is dedicated to:
All the maths teachers and education professionals I have worked with; you have all shaped my practice in some way that has led me to this point.
All of the maths teachers and education professionals I converse with on Twitter; you are a constant source of inspiration that challenges me to keep getting better. I am not going to try and list you all (we all know how that goes, Julia @TessMaths), so just know that I value our conversations and debates.
My mum, Lesley Mattock, who has been one of the greatest sources of support to me throughout my life and without whose help I would never have reached this point.
But mostly this book is dedicated to my loving partner Rowan. Her understanding and support throughout my career and throughout this project has been beyond what any man could hope for. She has put up with so much whilst I have worked to get to where I am in my career, and even more as I balanced leading a mathematics department with writing this book. Without her love this book would never have been written.
I also wish to offer my sincere thanks to:
Jonathan Hall (@StudyMaths) for his excellent website mathsbot.com and in particular for allowing me to use his virtual manipulatives as the basis with which to create the vast majority of the images used in this book.
Jan Parry, Dr Mark McCourt, Professor Anne Watson, Professor John Mason, Pete Griffin and Steve Lomax, all of whom between them have taught me the importance of actually having a personal pedagogy and opened my eyes to the importance of ensuring that pedagogy is well informed, as well as influencing my knowledge of representation, structure, variation theory and a host of other important approaches in an array (no pun intended!) of different ways.
David and Karen Bowman at Crown House Publishing for agreeing to publish this book and their encouragement throughout the process, as well as the support of their staff – particularly Louise Penny and Emma Tuck, who managed to take my ramblings and prompt me to create something coherent from them, Tom Fitton for the excellent illustrations, Rosalie Williams and Tabitha Palmer for dealing with all the marketing, and Beverley Randell for helping me navigate the process of actually taking a book from a collection of thoughts and ideas to something worthy of publication.
Contents
Introduction
There is a great mathematics story that I was told in a lecture at university. It involves two donkeys and a fly. The problem goes that two donkeys are 100 metres apart and walking directly towards each other at 1 metre per second. A fly starts on the nose of the first donkey and buzzes between the noses of the two donkeys at 10 metres per second. The question is, how long before the fly is crushed between the two donkeys?
One of the ways to solve this problem is summing an infinite series (i.e. summing the terms of a sequence that continues forever). On its way to the second donkey the fly is travelling for seconds, then on the way back seconds, then another seconds, and so on. The nth term of the geometric series is given by and so the sum to infinity of the series is seconds.
The other way to solve the problem is to ignore the fly completely. Each donkey is walking at 1 metre per second. This means that they will meet halfway at 50 metres. If they travel 50 metres at 1 metre per second it will take 50 seconds.
The story goes that a group of university students were told that a natural mathematician would automatically try to solve the problem using an infinite series and a natural physicist would solve it using the simpler approach. The problem therefore sorted mathematicians from physicists: if a student were able to solve it in a few seconds they were a physicist and if not they were a mathematician. The undergraduates were posing the problem to various students passing through the university library when the famous mathematician Leonhard Euler walked by. They presented the problem to Euler and were amazed when he answered the problem within a few seconds, as they had automatically expected him to begin considering the infinite series. When one of the students explained that a natural mathematician would have begun by forming the infinite series for the motion of the fly, Euler replied, ‘But that is what I did …’
A very similar story exists about the eminent mathematician and computer scientist John von Neumann and trains, which makes me suspect that this is at best a parable about Euler and at worst a case of Chinese whispers. However, the point of the story is not to show how good at mathematics Euler (or von Neumann) was, but instead to show that sometimes in mathematics the way you think about the calculation or problem you are solving has a great impact on how simple the problem is or how much sense it makes. Only the best A level mathematics students would be able to form the infinite series necessary to solve the problem, whereas most early secondary school pupils would be able to work out the simpler solution.
The importance of having different ways to view even the most simple mathematics, in order to build up to more complicated ideas, cannot be overstated. Some ways of thinking about numbers make some truths self-evident, whilst simultaneously obscuring others. In the same way in physics that it is sometimes better to view elementary matter as particles and at other times as waves, so in mathematics it is sometimes better to view numbers as discrete and at other times as continuous, as counters or bars, as tallies or vectors. Crucially for teachers, being explicit about how we are thinking about numbers and operations, and encouraging pupils to think about them in different ways, can add real power to their learning.
Much has been made of the effectiveness of metacognition in raising the attainment of pupils. For example, John Hattie lists metacognitive strategies as having an effect size of 0.6 in the most recent list of factors influencing student achievement.* Ofsted also recognises the importance of the use of manipulatives and representations to support flexibility in pupil thinking. In their Mathematics: Made to Measure report from 2012, it is noted that schools should choose ‘teaching approaches and activities that foster pupils’ deeper understanding, including through the use of practical resources, [and] visual images’.† In Improving Mathematics in Key Stages Two and Three, the Education Endowment Foundation lists ‘Use manipulatives and representations’ as one of its key recommendations.‡ It is therefore important that we give the pupils the tools they need in order to think about the mathematics they are working with in different ways.
The use of representations and structure is also an important part of teaching for mastery approaches. The National Centre for Excellence in the Teaching of Mathematics (NCETM) lists representation and structure as one of the ‘Five Big Ideas’ in teaching for mastery.§ The NCETM make clear that using appropriate representations in lessons can help to expose the mathematical structure being taught, allowing pupils to make connections between and across different areas of maths. They also emphasise that the aim in using these representations is that pupils will eventually understand enough about the structure such that they do not need to rely on the representation any more. This is often summarised as employing a concrete-pictorial-abstract (or CPA) approach to teaching mathematics.
Recently re-popularised in the UK following the focus on teaching approaches imported from places such as Shanghai and Singapore, the CPA approach actually has at least some of its roots in the 1982 Cockcroft Report, which reviewed the teaching of maths in England and Wales.¶ The Cockcroft Report advocated (among many other things) the need to allow pupils the opportunity of practical exploration with concrete materials before moving towards abstract thinking.
There are several studies on the use of manipulatives across the age and ability range, with most showing that mathematics achievement is increased through the long-term use of concrete materials. The most comprehensive of these is Sowell’s ‘Effects of Manipulative Materials in Mathematics Instruction’, a meta-analysis of 60 individual studies designed to determine the effectiveness of mathematics instruction with manipulative materials.|| Those surveyed ranged in age from pre-school children to college-age adults who were studying a variety of mathematics topics. Sowell found that ‘mathematics achievement is increased through the long-term use of concrete instructional materials and that students’ attitudes toward mathematics are improved when they have instruction with concrete materials provided by teachers knowledgeable about their use’.**
The aim of this book is to explore some of the different concrete materials available to teachers and pupils, ways of using these concrete and pictorial approaches to represent different types of numbers as discrete or continuous, how certain operations work when viewing numbers in these ways, and how these various representations can help to support the understanding of different concepts in mathematics. The book will look at the strengths of each representation, as well as the flaws, so that both primary and secondary school teachers of mathematics can make informed judgements about which representations will benefit their pupils. I will draw on my own experience of using the representations, as well as experiences shared by others, and appropriate research in order to support teachers in understanding how these representations can be implemented in the classroom.
How to use this book
I have often noticed that one of the difficulties pupils have in acquiring new mathematical understanding is that we introduce new ways of representing or thinking about mathematics at the same time as we try to teach a new mathematical concept or skill. I will take an alternative approach here, which is to explore all of the representations first and then, once they are secure, examine how more complicated calculations and concepts can be developed.
I wouldn’t introduce all of these representations at once with pupils; instead I would introduce two or three. Importantly, though, I would ensure that pupils are comfortable with the representation before trying to use the representation to explore a new concept. This generally involves introducing the representation to pupils within a concept they are comfortable with, and modelling with them how the representation fits with what they already know. This then allows the teacher to develop the concept into something new, using the representation as a bridge.
As this book is aimed at teachers, Chapter 1 will set out all of the representations within the secure concept of whole numbers, and Chapter 2 will then extend these representations to include fractions and decimals. The basic operations of addition and subtraction of whole numbers will be introduced in Chapter 3, followed by multiplication and division of whole numbers in Chapter 4, and powers and roots of whole numbers in Chapter 5. Chapter 6 then explores these ideas as applied to fractions and decimals. Chapter 7 examines the use of representations to illustrate the fundamental laws of arithmetic, and then in Chapter 8 we look at how these combine to define the correct order of operations in calculations involving multiple operations. Chapter 9 covers the concepts of accuracy, including rounding, significant figures and bounds, before we move on to irrational numbers in Chapter 10.
Chapter 11 sees the introduction of different representations applied to algebra, after which we progress to manipulating algebraic expressions by simplifying expressions (Chapter 12), multiplying expressions (Chapter 13) and expanding and factorising expressions (Chapter 14). In Chapter 15 we look at how representations can support with illustrating the solutions of equations, and then Chapter 16 examines some particular algebraic manipulations not covered in Chapters 12 to 14 – in particular, the difference of two squares and completing the square. Finally, Chapter 17 seeks to answer some of the questions about the use of representations in the classroom that may arise from the reading of the book.
You will notice while reading the book that some key mathematical terms are presented in bold – for your convenience these terms are defined in a glossary, found at the back of the book.
The fact that the book spans almost the complete breadth of primary and secondary school mathematics might make some question the usefulness of covering everything in one text. One reason I have chosen to do so is that I feel it is important that teachers understand not just the stage they are teaching, but also how this builds on what has been taught before and how this is built on in the stages after. This ensures that teachers see how what they are teaching fits into the wider pupil journey, and can support pupils no matter where they are along the way. Pupils will enter and leave stages of schooling at many different points, and just because we might teach in a secondary school doesn’t mean we won’t need to support pupils who haven’t secured concepts from primary school, or similarly that teachers in primary schools won’t need to provide depth in a topic by allowing pupils to explore a concept to a point that would normally be taught in secondary school. In this, all-through (3–18) schools have an advantage as they can design their curriculum to build all the way through the school. Those working in separate primary and secondary schools, or other school models, must use strong transition links to make this happen. So, for primary school teachers, this book showcases the mathematics you will teach and show you how it extends into secondary school. For secondary teachers, this book will provide some insight into approaches that might be used in feeder primaries and how you can develop them in secondary school.
I hope this book will support teachers in choosing suitable representations for use in their classrooms by making them much more secure in their own understanding of the strengths and weaknesses of each representation, but also, importantly, of how the representations highlight different interpretations of the concepts we explore with pupils. Some of the examples in the book will be suitable for direct use with pupils in the classroom, whilst some will be of more benefit to teachers in developing their own understanding. Pupils will very often need more than the one or two examples illustrated at each stage; in many cases, they will need to experience careful modelling with multiple examples as well as have the opportunity to explore concepts with the different manipulatives and representations provided. Only in this way will pupils eventually move beyond the representations.
The true aim of this book is for teachers to feel sufficiently confident in the use of the representations that they can explain enough about the underlying structures of the different concepts so that pupils no longer need to rely on the representations to see these structures. This is an important end goal for teachers to keep in mind – pupils should be aiming to move beyond the representation. Representations are tools that provide a window into the underlying structure of a concept. They are a window that pupils can keep coming back to look into, but they are not a window they should continually have to stare through. There is a danger that representations become another procedure that pupils have to remember and apply without understanding; this must be avoided at all costs if pupils are going to work towards mastery of mathematical concepts. This is why multiple representations are used for each concept, and why the literature makes clear the need for multiple representations to ensure pupils have a range of ways of thinking about concepts.
* See https://www.visiblelearningplus.com/sites/default/files/250%20Influences.pdf.
† Ofsted, Mathematics: Made to Measure (May 2012). Ref: 110159. Available at: https://www.gov.uk/government/publications/mathematics-made-to-measure, p. 10.
‡ See P. Henderson, J. Hodgen, C. Foster and D. Kuchemann, Improving Mathematics in Key Stages Two and Three: Guidance Report (London: Education Endowment Foundation, 2017). Available at: https://educationendowmentfoundation.org.uk/public/files/ Publications/Campaigns/Maths/KS2_KS3_Maths_Guidance_2017.pdf, pp. 10–13.
§ See https://www.ncetm.org.uk/resources/50042.
¶ W. H. Cockcroft (chair), Mathematics Counts: Report of the Committee of Inquiry into the Teaching of Mathematics in Schools [Cockcroft Report] (London: HMSO, 1982). Available at: http://www.educationengland.org.uk/ documents/cockcroft/cockcroft1982.html.
|| E. J. Sowell, Effects of Manipulative Materials in Mathematics Instruction, Journal for Research in Mathematics Education, 20(5) (1989), 498–505. Available at: http://www.jstor.org/stable/749423?read-now=1&seq=7#references_tab_contents.
** Sowell, Effects of Manipulative Materials in Mathematics Instruction, 498.
Chapter 1
Different representations of whole numbers
Many people believe that counting was the earliest mathematical concept to emerge. Whilst counting can be traced back several thousands of years, the first mathematical idea was actually the one-to-one relationship – relating a number of objects with an equal number of different objects. According to Kris Boulton, ancient shepherds would allow their sheep out to graze during the day, and for every sheep that went out they would put a stone into a pot. At the end of the day, the shepherds would bring the sheep back into the pens to keep them safe from predators. As each animal returned, the shepherds would remove a stone from the pot. When the pot was empty, all the sheep were safely back.* Interestingly, it seems that no concept was required for how many sheep there were, just that the number of sheep was equal to the number of stones.
The earliest example of counting itself is thought to be the Ishango bone, which bears scratch marks grouped in 60s. Discovered in Africa in 1960, the bone is believed to be more than 11,000 years old and is seen by many as the earliest example of a mathematical structure.† There is still not complete consensus about what these scratch marks represent, but one theory is that they are related to some form of lunar calendar. This would make sense given the prevalence of the number 60 in ancient time-keeping; indeed, our own 60-minute hour and 60-second minute can be traced back to the ancient Babylonians and their base 60 number system.
Both of these approaches treat numbers as discrete objects: you have one sheep, two sheep or three sheep (even though the shepherds weren’t actually counting them); you have one scratch, two scratches or three scratches. These earliest occurrences of numerical relationships are still relatable to a mathematical representation that we use today to show and track discrete values – tallying.
Tallying
Tallying is probably one of the most basic representations of discrete number. In the English national curriculum, tally charts are introduced in Year 2 (age 6–7), although they could be used as a pictorial representation of number in Year 1 or earlier. Children are often taught to count before entering any statutory stage of education, and in the Early Years Foundation Stage statutory framework it is required for pupils to ‘improve their skills in counting, understanding and using numbers, [and] calculating simple addition and subtraction problems’.‡
The use of one mark per item to count harks back all the way to the earliest one-to-one relationships, and is a representation of number that nearly all mathematics students can grasp. The basic tenet of the representation is that a vertical line is used to represent a discrete value (normally 1) and these are grouped together in 5s or 10s when counting large numbers:
It is very unusual for a tally mark to stand for anything other than 1, although theoretically it is possible (e.g. using pictograms to represent data takes advantage of this idea to represent large numbers). Tallying is severely deficient as a representation of number for anything other than the counting of a small discrete number of objects. Representing negative numbers is also problematic, to the point where no one would really consider using it. However, it is a valid representation of discrete number that can support young children to master counting and create a semi-permanent record, so its value should not be underestimated. Indeed, much medieval accounting was done using tallying – marks representing the value of goods or items traded or borrowed would be carved onto a piece of wood using large tally marks. The wood would then be split along its length so the notches appeared on each half. This provided both parties with a record of the trade that couldn’t be altered, and only those two pieces of wood could fit together to confirm they were records of the same trade. Students of mathematics should definitely be aware of tally marks as a representation for counting small discrete values, and possibly some of the history around them, but they should also be aware of the limitations of this representation in moving mathematics forward.
It wasn’t until the emergence of complex civilisations that more sophisticated views of numbers developed. As early as 4000 BC, the ancient Sumerians lived in cities, some of which may have had up to 80,000 residents. This required proper administration and consequently more sophisticated mathematics. Taxes needed to be collected and recorded, resources counted and measured, wealth calculated and compared. It is here that we see the birth of one of the more versatile discrete number representations – tokens, or counters.
Counters
Counters certainly have many advantages as a representation of discrete numbers when compared to tallying. It is much easier to assign different values to counters (think of the number of different value coins that have existed in various world currencies) and so take relationships beyond the one-to-one relationships that were a hallmark of very early mathematics and counting systems. The fact that counters can be removed, as well as added to, allows for the development of arithmetic, which was crucial in developing the mathematics required to manage the complex financial calculations needed to administrate a city.
In the mathematics classroom, counters can be used in a variety of ways to support pupils’ understanding of different types of numbers. At a simple level, counters can be used to represent positive integers in the same way that tallies do:
However, the versatility of counters more readily allows for them to hold different values, either by using different colour counters or ones that can be written on. For example, place value counters can be used to support an understanding of large numbers:
This allows large numbers to be represented without needing thousands of counters – for example:
In addition to representing larger numbers, counters also have an advantage over tallies in that they can simultaneously represent positive and negative numbers, which is done using either two different colours or, if available, double-sided counters:
The ability to use counters to simultaneously represent positive and negative numbers means that counters are an excellent way to develop directed number arithmetic. Crucial to this is the understanding that a ‘1’ counter plus a ‘-1’ counter results in 0. Indeed, a pair of these together (like the pair below) are often called a zero-pair.
Both tallies and counters have one crucial drawback, however: they only represent numbers as discrete quantities. In both cases it isn’t clear that there are numbers between 1 and 2, and whilst it is possible to represent fractions and decimals using counters once these concepts are well defined, it is very difficult to introduce the idea of either fractions or decimal numbers using solely counters or tallies. The first representation that begins to show numbers as both discrete and continuous is one very familiar representation – the number line.
The number line
As a discrete number representation, the number line shares many of the advantages that counters have over tallies, along with a few others. By representing numbers as positions along a line, we can build in 1s to any number without the need for an excessive number of counters to represent large numbers (assuming each counter has a value of 1).
It is also possible to represent numbers of different sizes simultaneously, as with place value counters, but with the added advantage that the relative sizes of the numbers are also shown clearly:
As they are not limited to place value divisions, the divisions on a number line (like counters) can take any discrete value:
This includes allowing for both positive and negative values simultaneously:
One of the major benefits of the number line representation is that it motivates the ‘between’ discussion (i.e. What is between 0 and 1? What is between 1 and 2?). Although using position on a number line is still a discrete view of number (we can only be in one position at a time), it begins to hint at the continuous nature of number – which is akin to the particle/wave duality in physics.
There are also drawbacks to the number line. The first is that it doesn’t actually develop the concept of number terribly well. Pupils need to have a relatively secure understanding of number to begin to work with a number line. It offers no secure reason why the symbol ‘2’ would have to follow the symbol ‘1’ or why ‘0’ represents nothingness. Pupil understanding of these concepts needs to be secure before the number line is introduced. However, we should consider carefully whether to wait to introduce the number line until we absolutely need it. As we saw in the introduction, introducing a representation at the point of need can be a major stumbling block for pupils. It may benefit learners if we were to first teach them about the concepts of ordinality and cardinality using counters, and only then explain how we can structure these numbers on a number line.
Ordered-pair graphs
A slight variation on the number line is to represent ordered-pairs on a two-dimensional graph. Although it is a bit more cumbersome than the number line, one advantage of the ordered-pair graph is that it shows the multiplicative relationships between pairs of values. For example, the graph below shows the number 2:
By plotting the point (1, 2) to show the number 2, and then drawing a line, it is possible to show that the multiplicative relationship between 1 and 2 is the same as the relationship between 2 and 4, 3 and 6 and so on, as all of these coordinates appear on the same line. This has obvious benefits when it comes to exploring division and fractions, as well as linking well to the concept of gradient.
Negative values can be represented in a similar way:
Like the number line, ordered-pair graphs show the duality of number – with a lean more towards the continuous in this example: although the number can be thought of as the plotted coordinate, it can also be considered as the whole line.
This representation does have its limitations, but it also allows for a different view of number which can highlight the properties of numbers that other representations often struggle to capture. The English national curriculum suggests that coordinates should first be introduced in Year 4, with full four-quadrant coordinate plotting in Year 6, although it would be understandable if this specific interpretation of numbers wasn’t introduced until secondary education.
Proportion diagrams
Another way of representing the multiplicative relationships between numbers is to use a proportion diagram. Many different forms of this diagram are used, but I prefer the one from the excellent ‘Improving Learning in Mathematics’ materials from the Department for Education and Skills (often known as the Standards Unit).§
Proportion diagrams are not, in fact, a true representation of number. They take the multiplicative relationships between numbers and highlight them, providing a straightforward way to demonstrate and develop proportional reasoning.
This diagram does not so much represent the number 2 as allow easy manipulation of the relationship between 2 and 1 – for example, to demonstrate that the relationship is the same as that between 6 and 3. Whilst this is not a representation of number as such, it is how ancient Greek mathematicians, such as Pythagoras, considered the universe – as being built out of the relationships between whole numbers (I doubt they used this exact diagram!). It was by considering these types of relationships that they were able to explain things like harmonies in music. One of Pythagoras’ many mathematical discoveries was that by fixing a string at simple ratios along its length, it was possible to create notes that were in harmony with the note produced by the original string. However, fixing a string at a point not corresponding to a simple ratio would produce a note out of harmony with the original note.
The proportion diagram will be useful later on when we come to explore fractions, decimals and operations between numbers.
Bar models
There are several approaches that attempt to capture the continuous nature of number that a number line begins to show, and perhaps the most well-known of these is the bar model:
One of the most familiar concrete tools for bar modelling are Cuisenaire rods. Cuisenaire is built on 10 different colour length rods, nominally having the values from 1 to 10. Other numbers can be built out of combinations of these rods. Due to their standard unit width, the rods can be combined end to end in order to represent numbers or combined along their length to create rectangles representing different numbers. They can also be stacked to create cuboids, which then use volume to represent numbers (although this is difficult to show visually when drawing bars).
Like counters, bars can take on different values. This can lead to some problems when using Cuisenaire rods to work with bars – for example, if the white rod represents the number 2 instead of 1, then only even numbers can be represented. This doesn’t happen when drawing bars. Teachers need to be aware of this limitation if they are working concretely with pupils to develop their most basic number concepts.
Bars are a very versatile representation as numbers can be represented using their length, area and volume. This allows us to combine bars in different ways, and makes them an ideal representation to explore many of the more developed concepts from the secondary maths curriculum. However, one difficulty with using bars is that it can be problematic to represent positive and negative values simultaneously. This can be dealt with, in part, by superimposing the bars onto a number line:
This bar shows 2 compared to -5, but without the number line it would probably be interpreted as 7 (5 and 2 added together).
When working concretely, the bars are usually compared side by side in order to show the relative values of the different bars (as in the diagram above or the left-hand diagram below). When working pictorially it can be beneficial to use a grid to break up the bars as in the right-hand diagram below.
Base ten blocks
Base ten blocks are a concrete mathematical manipulative designed to show place value and the power of 10 on which our decimal number system is built. For example, the blocks below combine to represent the number 134:
Like Cuisenaire rods, base ten blocks are designed to simultaneously show a discrete and continuous view of number, particularly highlighting the relationships in a base 10 number system. They can be used to represent numbers as length, area or volume (with the concrete version) across four different powers of 1 by combining 1s and 10s end to end, along edges to create area or stacking to create volume. The idea of an area and a length having the same numerical value is a very useful one when generalising properties and operations of number. The ability to use base ten blocks to show this by treating them in a similar way to place value counters makes them a beneficial, if not crucial, representation of number.
Like bars, one way this representation falls down is the simultaneous representation of both positive and negative numbers. Using blocks on a number line can help to overcome this problem in the same way that it does for Cuisenaire rods and bars, but this limits the representation to length only, because area and volume cannot show direction in the same way that displacement can.
This diagram shows the bars as a displacement away from 0, with the ‘10’ bar showing positive 10 and the three ‘1’ bars showing -3:
Here, the use of the number line limits us to using length, as the two-dimensional nature of the ‘100’ tile is not compatible with the one-dimensional number line:
A representation that can show the simultaneous representation of positive and negative numbers using a continuous rather than discrete view of number is vectors.
Vectors in one dimension
Whilst readers may be familiar with vectors in two or even three dimensions, many people may have never contemplated the parallels between directed number and one-dimensional vectors. However, if we consider a basic definition of a vector as an arrow representing a quantity with both magnitude and direction, then it is very quickly possible to discern their usefulness in representing numbers. Indeed, if you regularly work with complex numbers in an Argand diagram, you will recognise that these are simply complex numbers with no imaginary part.
This diagram shows the numbers 3 and -5.
Although losing the area and volume interpretations afforded by bars (Cuisenaire) and base ten blocks, this representation captures the duality of discrete numbers and continuous numbers perfectly – for example, the number 3 can be thought of simultaneously as the point at the end of the arrow and as the length of the arrow. This makes a vector representation ideal for demonstrating nearly all directed number calculations.
Whilst officially (according to the English national curriculum) the geometrical interpretation of vectors is not introduced until Key Stage 4 (when pupils are about 14 years old), I have found that pupils in Year 7 are comfortable with this representation due to their familiarity with number lines. Therefore, I suspect that vectors could be introduced even earlier than Year 7, often just changing jumps for arrows in the earlier stages. In fact, it is entirely possible that we could introduce this representation alongside number lines, so that rather than showing jumps on a number line, we show arrows doing the same job.
* Kris recounted this story in his presentation ‘The Stories of Mathematics – Part 1’ at the Complete Mathematics Conference 5, Sheffield, 26 September 2015.
† See http://www.math.buffalo.edu/mad/Ancient-Africa/ishango.html.
‡ Department for Education, Statutory Framework for the Early Years Foundation Stage: Setting the Standards for Learning, Development and Care for Children from Birth to Five (March 2017). Available at: https://www.gov.uk/government/publications/early-years-foundation-stage-framework--2, p. 8.
§ See http://webarchive.nationalarchives.gov.uk/20110505180928/ https://www.ncetm.org.uk//resources//1442.
Chapter 2
Representing fractions and decimals
Now that we have a clear understanding of the different representations that will be useful in exploring different facets of numbers and numerical relationships, it is time to begin developing the number system beyond the integers.
At this point, it is important to draw a distinction between representing a number and developing a concept. In the counters representation in Chapter 1
