This challenge is about finding the difference between numbers which have the same tens digit.

Can you make dice stairs using the rules stated? How do you know you have all the possible stairs?

Ben and his mum are planting garlic. Use the interactivity to help you find out how many cloves of garlic they might have had.

This task follows on from Build it Up and takes the ideas into three dimensions!

Frances and Rishi were given a bag of lollies. They shared them out evenly and had one left over. How many lollies could there have been in the bag?

Only one side of a two-slice toaster is working. What is the quickest way to toast both sides of three slices of bread?

How many ways can you find to do up all four buttons on my coat? How about if I had five buttons? Six ...?

Two children made up a game as they walked along the garden paths. Can you find out their scores? Can you find some paths of your own?

Can you find all the ways to get 15 at the top of this triangle of numbers? Many opportunities to work in different ways.

This challenge focuses on finding the sum and difference of pairs of two-digit numbers.

Find the sum and difference between a pair of two-digit numbers. Now find the sum and difference between the sum and difference! What happens?

In a Magic Square all the rows, columns and diagonals add to the 'Magic Constant'. How would you change the magic constant of this square?

What can you say about these shapes? This problem challenges you to create shapes with different areas and perimeters.

Watch this animation. What do you notice? What happens when you try more or fewer cubes in a bundle?

Sweets are given out to party-goers in a particular way. Investigate the total number of sweets received by people sitting in different positions.

An investigation that gives you the opportunity to make and justify predictions.

This challenge, written for the Young Mathematicians' Award, invites you to explore 'centred squares'.

Tom and Ben visited Numberland. Use the maps to work out the number of points each of their routes scores.

This challenge encourages you to explore dividing a three-digit number by a single-digit number.

While we were sorting some papers we found 3 strange sheets which seemed to come from small books but there were page numbers at the foot of each page. Did the pages come from the same book?

Find the sum of all three-digit numbers each of whose digits is odd.

Try out this number trick. What happens with different starting numbers? What do you notice?

We can arrange dots in a similar way to the 5 on a dice and they usually sit quite well into a rectangular shape. How many altogether in this 3 by 5? What happens for other sizes?

Try adding together the dates of all the days in one week. Now multiply the first date by 7 and add 21. Can you explain what happens?

Polygonal numbers are those that are arranged in shapes as they enlarge. Explore the polygonal numbers drawn here.

In this calculation, the box represents a missing digit. What could the digit be? What would the solution be in each case?

What happens when you round these three-digit numbers to the nearest 100?

Does this 'trick' for calculating multiples of 11 always work? Why or why not?

Compare the numbers of particular tiles in one or all of these three designs, inspired by the floor tiles of a church in Cambridge.

How many different journeys could you make if you were going to visit four stations in this network? How about if there were five stations? Can you predict the number of journeys for seven stations?

Find out what a "fault-free" rectangle is and try to make some of your own.

Can you see why 2 by 2 could be 5? Can you predict what 2 by 10 will be?

How can you arrange these 10 matches in four piles so that when you move one match from three of the piles into the fourth, you end up with the same arrangement?

In how many different ways can you break up a stick of 7 interlocking cubes? Now try with a stick of 8 cubes and a stick of 6 cubes.

Put the numbers 1, 2, 3, 4, 5, 6 into the squares so that the numbers on each circle add up to the same amount. Can you find the rule for giving another set of six numbers?

Can you continue this pattern of triangles and begin to predict how many sticks are used for each new "layer"?

Can you dissect an equilateral triangle into 6 smaller ones? What number of smaller equilateral triangles is it NOT possible to dissect a larger equilateral triangle into?

Are these statements relating to odd and even numbers always true, sometimes true or never true?

This problem challenges you to find out how many odd numbers there are between pairs of numbers. Can you find a pair of numbers that has four odds between them?

Find a route from the outside to the inside of this square, stepping on as many tiles as possible.

Take a look at the video of this trick. Can you perform it yourself? Why is this maths and not magic?

Watch this film carefully. Can you find a general rule for explaining when the dot will be this same distance from the horizontal axis?

This activity involves rounding four-digit numbers to the nearest thousand.

This challenge asks you to imagine a snake coiling on itself.

Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?

Investigate the sum of the numbers on the top and bottom faces of a line of three dice. What do you notice?

Take a counter and surround it by a ring of other counters that MUST touch two others. How many are needed?

Use your addition and subtraction skills, combined with some strategic thinking, to beat your partner at this game.

Use the interactivity to investigate what kinds of triangles can be drawn on peg boards with different numbers of pegs.