Florence, Ethan and Alma have each added together two 'next-door' numbers. What is the same about their answers?

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

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?

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

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?

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?

If there are 3 squares in the ring, can you place three different numbers in them so that their differences are odd? Try with different numbers of squares around the ring. What do you notice?

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

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

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

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.

These spinners will give you the tens and unit digits of a number. Can you choose sets of numbers to collect so that you spin six numbers belonging to your sets in as few spins as possible?

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?

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

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

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?

Yasmin and Zach have some bears to share. Which numbers of bears can they share so that there are none left over?

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

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

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

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

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

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

Ben’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?

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

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?

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

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

Can you sort numbers into sets? Can you give each set a name?

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.

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.

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.

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.

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

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?

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

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.

I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?

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.

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 interactivities to fill in these Carroll diagrams. How do you know where to place the numbers?

Think of a number, square it and subtract your starting number. Is the number you’re left with odd or even? How do the images help to explain this?

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

How have the numbers been placed in this Carroll diagram? Which labels would you put on each row and column?

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