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?
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.
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
Explore the relationship between simple linear functions and their graphs.
Follow the clues to find the mystery number.
Number problems at primary level to work on with others.
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.
This is a game for two players. What must you subtract to remove the rolled digit from your number? The first to zero wins!
Number problems at primary level that may require resilience.
Who said that adding couldn't be fun?
Visitors to Earth from the distant planet of Zub-Zorna were amazed when they found out that when the digits in this multiplication were reversed, the answer was the same! Find a way to explain. . . .
Each child in Class 3 took four numbers out of the bag. Who had made the highest even number?
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. . . .
Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?
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.
Use your knowledge of place value to try to win this game. How will you maximise your score?
Start by putting one million (1 000 000) into the display of your calculator. Can you reduce this to 7 using just the 7 key and add, subtract, multiply, divide and equals as many times as you like?
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?
Find the values of the nine letters in the sum: FOOT + BALL = GAME
Try out this number trick. What happens with different starting numbers? What do you notice?
Number problems at primary level that require careful consideration.
By selecting digits for an addition grid, what targets can you make?
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?
Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
Can you work out some different ways to balance this equation?
There are six numbers written in five different scripts. Can you sort out which is which?
Have a go at balancing this equation. Can you find different ways of doing it?
This article for primary teachers encourages exploration of two fundamental ideas, exchange and 'unitising', which will help children become more fluent when calculating.
This article develops the idea of 'ten-ness' as an important element of place value.
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.
These tasks will help learners develop their understanding of place value, particularly giving them opportunities to express numbers as amounts.
This feature aims to support you in developing children's early number sense and understanding of place value.
More upper primary number sense and place value tasks.
Dicey Operations for an adult and child. Can you get close to 1000 than your partner?
Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your opponent.
What happens when you add a three digit number to its reverse?
There are nasty versions of this dice game but we'll start with the nice ones...
Try out some calculations. Are you surprised by the results?
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.
Can you replace the letters with numbers? Is there only one solution in each case?
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?
How many positive integers less than or equal to 4000 can be written down without using the digits 7, 8 or 9?
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. . . .
In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?
Find the sum of all three-digit numbers each of whose digits is odd.