Copyright © University of Cambridge. All rights reserved.
Why do this problem?
Introducing humour into maths does add to the enjoyment - and the children will find this activity
funny. It is a good opportunity for them to practise counting and to record findings in different ways. And there's the added bonus that everyone could have a different answer and be right. Learners will need to
find strategies to keep track of where they have got to in terms of numbers of legs and to regulate and readjust as they get close to twelve.
Cross curricular links can be made by using the story of Noah and the ark as an introduction. Considering creatures with one 'leg' such as slugs and snails, no legs such as snakes and all the other possibilities is great fun and provokes interesting responses from the children. You may be surprised by their ingenuity.
You could either precede or follow this investigation by reading the book 'One is a Snail, Ten is a Crab - A Counting by Feet Book' by April Pulley Sayre and Jeff Sayre (published by Candlewick Press, 2003 ISBN 0-7636-1406-8), in which counting right up to a hundred is achieved through combinations of snails, people, dogs, insects, spiders and crabs.
But if you can't get hold of it, it's worth doing this as a whole class activity.
- Ask for suggestions and encourage the children to come to the board and draw their animals. Count the number of creatures each child draws and discuss who has drawn the least, the most, the same as ... etc.
- Give the children playdough and 12 equal lengths of straw each so that they can make the creatures - and put them into groups of 12 legs for a display.
- Let each child draw a picture, write the number sentence below it (eg $6 \: + \:4 \; + \; 2 \; = \; 12$) and make them all into a class zig-zag book - Our Story of Twelve.
- Give each group of children a different number of legs to investigate and ask them to make their own group zig-zag book.
Alternatively, you may wish to show this poster
of two possible animals that Noah might have seen. You could start by asking what is the same and what is different about the two animals and then encourage the children to think of other animals with different numbers of legs. Learners could draw their own animals, or cut them out from
. (Thank you to Mark Dawes for the files and to Emily for the drawings.)
What creatures could there be?
How many legs do they each have?
What's the greatest number of creatures he could have seen?
What's the smallest number of creatures he could have seen?
You could ask questions such as: What if ... there were twelve creatures? How many legs could that be?
What if there were more legs... 18, 24, 19 ... or fewer?
Giving children 12 straws for legs and modelling clay will support them to think about the ways they might use the 12 legs to make a range of different creatures that use up their legs.