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?

How would you create the largest possible two-digit even number from the digit I've given you and one of your choice?

Pat counts her sweets in different groups and both times she has some left over. How many sweets could she have had?

Look at what happens when you take a number, square it and subtract your answer. What kind of number do you get? Can you prove it?

Can you find the chosen number from the grid using the clues?

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.

How many legs do each of these creatures have? How many pairs is that?

Becky created a number plumber which multiplies by 5 and subtracts 4. What do you notice about the numbers that it produces? Can you explain your findings?

This article for teachers describes how number arrays can be a useful reprentation for many number concepts.

Daisy and Akram were making number patterns. Daisy was using beads that looked like flowers and Akram was using cube bricks. First they were counting in twos.

Each child in Class 3 took four numbers out of the bag. Who had made the highest even number?

Four of these clues are needed to find the chosen number on this grid and four are true but do nothing to help in finding the number. Can you sort out the clues and find the number?

In this problem we are looking at sets of parallel sticks that cross each other. What is the least number of crossings you can make? And the greatest?

Investigate which numbers make these lights come on. What is the smallest number you can find that lights up all the lights?

You can trace over all of the diagonals of a pentagon without lifting your pencil and without going over any more than once. Can the same thing be done with a hexagon or with a heptagon?

This activity is best done with a whole class or in a large group. Can you match the cards? What happens when you add pairs of the numbers together?

These red, yellow and blue spinners were each spun 45 times in total. Can you work out which numbers are on each spinner?

If you have ten counters numbered 1 to 10, how many can you put into pairs that add to 10? Which ones do you have to leave out? Why?

Arrange the numbers 1 to 6 in each set of circles below. The sum of each side of the triangle should equal the number in its centre.

Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?

This investigates one particular property of number by looking closely at an example of adding two odd numbers together.

How many different sets of numbers with at least four members can you find in the numbers in this box?

Try to stop your opponent from being able to split the piles of counters into unequal numbers. Can you find a strategy?

There are ten children in Becky's group. Can you find a set of numbers for each of them? Are there any other sets?

Are these statements always true, sometimes true or never true?

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

A game for 2 or more people. Starting with 100, subratct a number from 1 to 9 from the total. You score for making an odd number, a number ending in 0 or a multiple of 6.

A game for 2 people using a pack of cards Turn over 2 cards and try to make an odd number or a multiple of 3.

This problem looks at how one example of your choice can show something about the general structure of multiplication.

Benâ€™s class were cutting up number tracks. First they cut them into twos and added up the numbers on each piece. What patterns could they see?

Use cubes to continue making the numbers from 7 to 20. Are they sticks, rectangles or squares?

There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?

Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.

Mr Gilderdale is playing a game with his class. What rule might he have chosen? How would you test your idea?

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

In this game for two players, the idea is to take it in turns to choose 1, 3, 5 or 7. The winner is the first to make the total 37.

This article introduces the idea of generic proof for younger children and illustrates how one example can offer a proof of a general result through unpacking its underlying structure.

What happens when you add three numbers together? Will your answer be odd or even? How do you know?

Choose four of the numbers from 1 to 9 to put in the squares so that the differences between joined squares are odd.

Use the interactivity to sort these numbers into sets. Can you give each set a name?

Can you put the numbers 1-5 in the V shape so that both 'arms' have the same total?

You have 4 red and 5 blue counters. How many ways can they be placed on a 3 by 3 grid so that all the rows columns and diagonals have an even number of red counters?

Try grouping the dominoes in the ways described. Are there any left over each time? Can you explain why?

Four bags contain a large number of 1s, 3s, 5s and 7s. Pick any ten numbers from the bags above so that their total is 37.

Use the interactivities to complete these Venn diagrams.