Think of a number and follow my instructions. Tell me your answer, and I'll tell you what you started with! Can you explain how I know?

How many pairs of numbers can you find that add up to a multiple of 11? Do you notice anything interesting about your results?

Imagine we have four bags containing numbers from a sequence. What numbers can we make now?

Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?

Think of two whole numbers under 10, and follow the steps. I can work out both your numbers very quickly. How?

When number pyramids have a sequence on the bottom layer, some interesting patterns emerge...

15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?

Can you find rectangles where the value of the area is the same as the value of the perimeter?

Which set of numbers that add to 10 have the largest product?

Can you find any two-digit numbers that satisfy all of these statements?

Try entering different sets of numbers in the number pyramids. How does the total at the top change?

My two digit number is special because adding the sum of its digits to the product of its digits gives me my original number. What could my number be?

What's the largest volume of box you can make from a square of paper?

How many winning lines can you make in a three-dimensional version of noughts and crosses?

Start with two numbers and generate a sequence where the next number is the mean of the last two numbers...

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

A country has decided to have just two different coins, 3z and 5z coins. Which totals can be made? Is there a largest total that cannot be made? How do you know?

You'll need to know your number properties to win a game of Statement Snap...

Imagine you have a large supply of 3kg and 8kg weights. How many of each weight would you need for the average (mean) of the weights to be 6kg? What other averages could you have?

Where should you start, if you want to finish back where you started?

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

What is the greatest volume you can get for a rectangular (cuboid) parcel if the maximum combined length and girth are 2 metres?

If you move the tiles around, can you make squares with different coloured edges?

A tilted square is a square with no horizontal sides. Can you devise a general instruction for the construction of a square when you are given just one of its sides?

I'm thinking of a rectangle with an area of 24. What could its perimeter be?

Can you recreate squares and rhombuses if you are only given a side or a diagonal?

Can you find a relationship between the number of dots on the circle and the number of steps that will ensure that all points are hit?

Imagine you were given the chance to win some money... and imagine you had nothing to lose...

Six balls are shaken. You win if at least one red ball ends in a corner. What is the probability of winning?

Seven balls are shaken. You win if the two blue balls end up touching. What is the probability of winning?

Alison and Charlie are playing a game. Charlie wants to go first so Alison lets him. Was that such a good idea?

Play around with sets of five numbers and see what you can discover about different types of average...

There are lots of different methods to find out what the shapes are worth - how many can you find?

Semi-regular tessellations combine two or more different regular polygons to fill the plane. Can you find all the semi-regular tessellations?

How well can you estimate 10 seconds? Investigate with our timing tool.

An aluminium can contains 330 ml of cola. If the can's diameter is 6 cm what is the can's height?

Interior angles can help us to work out which polygons will tessellate. Can we use similar ideas to predict which polygons combine to create semi-regular solids?

Can you make a right-angled triangle on this peg-board by joining up three points round the edge?

Identical squares of side one unit contain some circles shaded blue. In which of the four examples is the shaded area greatest?

There are nasty versions of this dice game but we'll start with the nice ones...

Who said that adding, subtracting, multiplying and dividing couldn't be fun?

Which countries have the most naturally athletic populations?