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?
Each child in Class 3 took four numbers out of the bag. Who had made the highest even number?
Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?
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?
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?
Who said that adding couldn't be fun?
A school song book contains 700 songs. The numbers of the songs are displayed by combining special small single-digit boards. What is the minimum number of small boards that is needed?
Using balancing scales what is the least number of weights needed to weigh all integer masses from 1 to 1000? Placing some of the weights in the same pan as the object how many are needed?
Can you replace the letters with numbers? Is there only one solution in each case?
There are six numbers written in five different scripts. Can you sort out which is which?
What is the sum of all the digits in all the integers from one to one million?
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?
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. . . .
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.
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
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?
Number problems at primary level that may require resilience.
Number problems at primary level that require careful consideration.
Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?
What happens when you round these three-digit numbers to the nearest 100?
What happens when you round these numbers to the nearest whole number?
Have a go at balancing this equation. Can you find different ways of doing it?
Dicey Operations for an adult and child. Can you get close to 1000 than your partner?
Try out some calculations. Are you surprised by the results?
Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your opponent.
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?
Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.
Number problems for inquiring primary learners.
Number problems at primary level to work on with others.
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
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?
Think of a two digit number, reverse the digits, and add the numbers together. Something special happens...
Explore the relationship between simple linear functions and their graphs.
We are used to writing numbers in base ten, using 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Eg. 75 means 7 tens and five units. This article explains how numbers can be written in any number base.
Amazing as it may seem the three fives remaining in the following `skeleton' are sufficient to reconstruct the entire long division sum.
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)?
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. . . .
Carry out cyclic permutations of nine digit numbers containing the digits from 1 to 9 (until you get back to the first number). Prove that whatever number you choose, they will add to the same total.
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.
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. . . .
How many solutions can you find to this sum? Each of the different letters stands for a different number.
Take the numbers 1, 2, 3, 4 and 5 and imagine them written down in every possible order to give 5 digit numbers. Find the sum of the resulting numbers.
How many positive integers less than or equal to 4000 can be written down without using the digits 7, 8 or 9?
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
How many six digit numbers are there which DO NOT contain a 5?
Find the values of the nine letters in the sum: FOOT + BALL = GAME
Follow the clues to find the mystery number.