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?

The value of the circle changes in each of the following problems. Can you discover its value in each problem?

Rocco ran in a 200 m race for his class. Use the information to find out how many runners there were in the race and what Rocco's finishing position was.

There are three buckets each of which holds a maximum of 5 litres. Use the clues to work out how much liquid there is in each bucket.

Explore Alex's number plumber. What questions would you like to ask? What do you think is happening to the numbers?

Peter, Melanie, Amil and Jack received a total of 38 chocolate eggs. Use the information to work out how many eggs each person had.

Use the information to work out how many gifts there are in each pile.

On a calculator, make 15 by using only the 2 key and any of the four operations keys. How many ways can you find to do it?

Can you score 100 by throwing rings on this board? Is there more than way to do it?

On the table there is a pile of oranges and lemons that weighs exactly one kilogram. Using the information, can you work out how many lemons there are?

What happens when you add the digits of a number then multiply the result by 2 and you keep doing this? You could try for different numbers and different rules.

This group activity will encourage you to share calculation strategies and to think about which strategy might be the most efficient.

Where can you draw a line on a clock face so that the numbers on both sides have the same total?

On the planet Vuv there are two sorts of creatures. The Zios have 3 legs and the Zepts have 7 legs. The great planetary explorer Nico counted 52 legs. How many Zios and how many Zepts were there?

If the numbers 5, 7 and 4 go into this function machine, what numbers will come out?

Find out what a Deca Tree is and then work out how many leaves there will be after the woodcutter has cut off a trunk, a branch, a twig and a leaf.

This number has 903 digits. What is the sum of all 903 digits?

Use 4 four times with simple operations so that you get the answer 12. Can you make 15, 16 and 17 too?

Put operations signs between the numbers 3 4 5 6 to make the highest possible number and lowest possible number.

56 406 is the product of two consecutive numbers. What are these two numbers?

Here are the prices for 1st and 2nd class mail within the UK. You have an unlimited number of each of these stamps. Which stamps would you need to post a parcel weighing 825g?

Put a number at the top of the machine and collect a number at the bottom. What do you get? Which numbers get back to themselves?

The Scot, John Napier, invented these strips about 400 years ago to help calculate multiplication and division. Can you work out how to use Napier's bones to find the answer to these multiplications?

Can you work out some different ways to balance this equation?

What is the lowest number which always leaves a remainder of 1 when divided by each of the numbers from 2 to 10?

Well now, what would happen if we lost all the nines in our number system? Have a go at writing the numbers out in this way and have a look at the multiplications table.

This task combines spatial awareness with addition and multiplication.

Use your logical reasoning to work out how many cows and how many sheep there are in each field.

Number problems at primary level that may require determination.

Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?

Have a go at balancing this equation. Can you find different ways of doing it?

Amy has a box containing domino pieces but she does not think it is a complete set. She has 24 dominoes in her box and there are 125 spots on them altogether. Which of her domino pieces are missing?

There are over sixty different ways of making 24 by adding, subtracting, multiplying and dividing all four numbers 4, 6, 6 and 8 (using each number only once). How many can you find?

The clockmaker's wife cut up his birthday cake to look like a clock face. Can you work out who received each piece?

Annie cut this numbered cake into 3 pieces with 3 cuts so that the numbers on each piece added to the same total. Where were the cuts and what fraction of the whole cake was each piece?

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?

Grandma found her pie balanced on the scale with two weights and a quarter of a pie. So how heavy was each pie?

Work out Tom's number from the answers he gives his friend. He will only answer 'yes' or 'no'.

Chandrika was practising a long distance run. Can you work out how long the race was from the information?

Can you design a new shape for the twenty-eight squares and arrange the numbers in a logical way? What patterns do you notice?

This article for teachers looks at how teachers can use problems from the NRICH site to help them teach division.

Look on the back of any modern book and you will find an ISBN code. Take this code and calculate this sum in the way shown. Can you see what the answers always have in common?

Find at least one way to put in some operation signs (+ - x ÷) to make these digits come to 100.

Number problems at primary level that require careful consideration.

Use this grid to shade the numbers in the way described. Which numbers do you have left? Do you know what they are called?

There were 22 legs creeping across the web. How many flies? How many spiders?