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### Number and algebra

### Geometry and measure

### Probability and statistics

### Working mathematically

### Advanced mathematics

### For younger learners

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### Your Number Is...

### Diagonal Sums

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Age 7 to 11

Challenge Level

- Problem
- Getting Started
- Teachers' Resources

Can you use the windows in the picture as a starting point?

What size window will you try next?

How will you remember what you have found out so far?

What size window will you try next?

How will you remember what you have found out so far?

Think of a number and follow the machine's instructions... I know what your number is! Can you explain how I know?

In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?