**We have chosen a selection of our favourite NRICH resources that challenge you to work systematically.**

Here are a few questions you might need to ask along the way:

Which piece of information is the most useful to start with? What next?

How will I record my findings?

Will I be confident that I have found all the results by the end?

The problems can be tackled in any order.

### Two and Two

How many solutions can you find to this sum? Each of the different letters stands for a different number.

### 1 Step 2 Step

### ACE, TWO, THREE...

### Isosceles Triangles

### M, M and M

If you are given the mean, median and mode of five positive whole numbers, can you find the numbers?

### Can they be equal?

### Sticky Numbers

### Shifting Times Tables

Can you find a way to identify times tables after they have been shifted up or down?

### Charlie's delightful machine

Here is a machine with four coloured lights. Can you develop a strategy to work out the rules controlling each light?