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?

How many solutions can you find to this sum? Each of the different letters stands for a different number.

Try out some calculations. Are you surprised by the results?

Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.

There are six numbers written in five different scripts. Can you sort out which is which?

Find the values of the nine letters in the sum: FOOT + BALL = GAME

How many more miles must the car travel before the numbers on the milometer and the trip meter contain the same digits in the same order?

Can you arrange the digits 1,2,3,4,5,6,7,8,9 into three 3-digit numbers such that their total is close to 1500?

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

Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. . . .

This addition sum uses all ten digits 0, 1, 2...9 exactly once. Find the sum and show that the one you give is the only possibility.

The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?

Consider all two digit numbers (10, 11, . . . ,99). In writing down all these numbers, which digits occur least often, and which occur most often ? What about three digit numbers, four digit numbers. . . .

The number 27 is special because it is three times the sum of its digits 27 = 3 (2 + 7). Find some two digit numbers that are SEVEN times the sum of their digits (seven-up numbers)?

Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?

Choose any 3 digits and make a 6 digit number by repeating the 3 digits in the same order (e.g. 594594). Explain why whatever digits you choose the number will always be divisible by 7, 11 and 13.

How many positive integers less than or equal to 4000 can be written down without using the digits 7, 8 or 9?

Think of any three-digit number. Repeat the digits. The 6-digit number that you end up with is divisible by 91. Is this a coincidence?

Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.

This article for primary teachers expands on the key ideas which underpin early number sense and place value, and suggests activities to support learners as they get to grips with these ideas.

In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?

Number problems for inquiring primary learners.

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

Nowadays the calculator is very familiar to many of us. What did people do to save time working out more difficult problems before the calculator existed?

Pick the number of times a week that you eat chocolate. This number must be more than one but less than ten. Multiply this number by 2. Add 5 (for Sunday). Multiply by 50... Can you explain why it. . . .

The Number Jumbler can always work out your chosen symbol. Can you work out how?

A school song book contains 700 songs. The numbers of the songs are displayed by combining special small single-digit cards. What is the minimum number of small cards that is needed?

Number problems at primary level that may require resilience.

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?

Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?

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

Replace the letters with numbers to make the addition work out correctly. R E A D + T H I S = P A G E

Alf describes how the Gattegno chart helped a class of 7-9 year olds gain an awareness of place value and of the inverse relationship between multiplication and division.

The number 3723(in base 10) is written as 123 in another base. What is that base?

Watch our videos of multiplication methods that you may not have met before. Can you make sense of them?

How many six digit numbers are there which DO NOT contain a 5?

More upper primary number sense and place value tasks.

This feature aims to support you in developing children's early number sense and understanding of place value.

Write down a three-digit number Change the order of the digits to get a different number Find the difference between the two three digit numbers Follow the rest of the instructions then try. . . .

One of the key ideas associated with place value is that the position of a digit affects its value. These activities support children in understanding this idea.

There are two forms of counting on Vuvv - Zios count in base 3 and Zepts count in base 7. One day four of these creatures, two Zios and two Zepts, sat on the summit of a hill to count the legs of. . . .

This article develops the idea of 'ten-ness' as an important element of place value.

When asked how old she was, the teacher replied: My age in years is not prime but odd and when reversed and added to my age you have a perfect square...

These tasks will help learners develop their understanding of place value, particularly giving them opportunities to express numbers as amounts.

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

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

Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your opponent.