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This investigation is likely to capture the attention of many children and you might discover that they find things to explore which had not occurred to you! It is also an enriching activity that has links both with spatial awareness, number awareness and number patterns. It could be used to broaden pupils'
experiences of number relationships.

You could introduce this investigation by drawing a caterpillar on a grid, perhaps on the interactive whiteboard, to establish the context. Invite a child to draw a different caterpillar on another grid and then ask pairs to talk about what they notice.

This leads into the first activity so this could be pursued further by the group, or some might prefer to opt for the second activity. You will need to have some conversations about how they might record what they have found. Having squared paper available, or perhaps some templates of different sized grids, would be a good idea, but children might have their own suggestions.

What do you see?

Tell me about the numbers you've.

I like this shape of caterpiller you've made, tell me about it.

Alan Parr (who has contributed many fantastic ideas to NRICH), also sent the following suggestions for investigating the Caterpillars in other ways:

- If a caterpillar has some segments which are black then you won't be able to see their numbers, so you can offer problems with missing numbers. You can have a surprisingly large number of missing numbers and still be able to fill in every one. For example, in caterpillar A you only need to know the $1, 5, 10,$ and $11$ and you can place all the other numbers. You could challenge children to fill in the rest of the numbers, but also invite them to make their own so that they give as few numbers as possible in order for a friend to be able to complete the caterpillar. You could also extend this to larger caterpillars!
- For a tougher challenge, you could change the caterpillars so that you can't see the individual segments, only four mega-sections each of which covers four segments in a $2 \times 2$ square. Each mega-section shows you the product of the four segments of the caterpillar. For example, the top-left quarter shows $24$, top-right $7920$, bottom-right $15288$, bottom-left $7200$. Can learners identify the number of each segment? (Alan attributes this idea to Mike Taylor - thank you!) You could also set this up in a "battleships-style" game where each player records a caterpillar in a square grid and player $1$ tells player $2$ the products of $2\times2$ blocks he/she asks about, and vice versa.

Here are some ideas to use if the pupils are new to the exploration of number patterns:

These show:

Adding horizontally, then vertically;

Adding in slanting lines - when you've done the two different sets, [North West to South East and then North East to South West] you can put them together in different ways;

Adding in squares and putting down the answer in a square. So, adding in a $2$ by $2$ square and performing all $9$ additions we would have:

There are lots of questions to be asked here, based on trying to explain the resulting totals.

Adding in $3$ by $3$ squares as above.