Follow this recipe for sieving numbers and see what interesting patterns emerge.
Can you make lines of Cuisenaire rods that differ by 1?
Which pairs of cogs let the coloured tooth touch every tooth on the other cog? Which pairs do not let this happen? Why?
How many integers between 1 and 1200 are NOT multiples of any of the numbers 2, 3 or 5?
Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?
Data is sent in chunks of two different sizes - a yellow chunk has 5 characters and a blue chunk has 9 characters. A data slot of size 31 cannot be exactly filled with a combination of yellow and. . . .
Is there an efficient way to work out how many factors a large number has?
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?
Lyndon chose this as one of his favourite problems. It is accessible but needs some careful analysis of what is included and what is not. A systematic approach is really helpful.
In how many ways can the number 1 000 000 be expressed as the product of three positive integers?
Can you find a relationship between the number of dots on the circle and the number of steps that will ensure that all points are hit?
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.
6! = 6 x 5 x 4 x 3 x 2 x 1. The highest power of 2 that divides exactly into 6! is 4 since (6!) / (2^4 ) = 45. What is the highest power of two that divides exactly into 100!?
Can you work out what size grid you need to read our secret message?
Given the products of adjacent cells, can you complete this Sudoku?
Factor track is not a race but a game of skill. The idea is to go round the track in as few moves as possible, keeping to the rules.
Using the digits 1 to 9, the number 4396 can be written as the product of two numbers. Can you find the factors?
A number N is divisible by 10, 90, 98 and 882 but it is NOT divisible by 50 or 270 or 686 or 1764. It is also known that N is a factor of 9261000. What is N?
Explain why the arithmetic sequence 1, 14, 27, 40, ... contains many terms of the form 222...2 where only the digit 2 appears.
The number 8888...88M9999...99 is divisible by 7 and it starts with the digit 8 repeated 50 times and ends with the digit 9 repeated 50 times. What is the value of the digit M?
What is the remainder when 2^2002 is divided by 7? What happens with different powers of 2?
Take any pair of numbers, say 9 and 14. Take the larger number, fourteen, and count up in 14s. Then divide each of those values by the 9, and look at the remainders.
What is the largest number which, when divided into 1905, 2587, 3951, 7020 and 8725 in turn, leaves the same remainder each time?
Do you know a quick way to check if a number is a multiple of two? How about three, four or six?
Find the number which has 8 divisors, such that the product of the divisors is 331776.
Can you find any perfect numbers? Read this article to find out more...
A collection of resources to support work on Factors and Multiples at Secondary level.
I'm thinking of a number. My number is both a multiple of 5 and a multiple of 6. What could my number be?
Find the highest power of 11 that will divide into 1000! exactly.
Can you find any two-digit numbers that satisfy all of these statements?
Play this game and see if you can figure out the computer's chosen number.
The five digit number A679B, in base ten, is divisible by 72. What are the values of A and B?
Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.
The number 12 = 2^2 × 3 has 6 factors. What is the smallest natural number with exactly 36 factors?
The flow chart requires two numbers, M and N. Select several values for M and try to establish what the flow chart does.
A game for two people, or play online. Given a target number, say 23, and a range of numbers to choose from, say 1-4, players take it in turns to add to the running total to hit their target.
Each letter represents a different positive digit AHHAAH / JOKE = HA What are the values of each of the letters?
Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?
How many zeros are there at the end of the number which is the product of first hundred positive integers?
Great Granddad is very proud of his telegram from the Queen congratulating him on his hundredth birthday and he has friends who are even older than he is... When was he born?
This article takes the reader through divisibility tests and how they work. An article to read with pencil and paper to hand.
Given the products of diagonally opposite cells - can you complete this Sudoku?
Find the smallest positive integer N such that N/2 is a perfect cube, N/3 is a perfect fifth power and N/5 is a perfect seventh power.
Factors and Multiples game for an adult and child. How can you make sure you win this game?
Consider numbers of the form un = 1! + 2! + 3! +...+n!. How many such numbers are perfect squares?
How did the the rotation robot make these patterns?
A game in which players take it in turns to choose a number. Can you block your opponent?