Filter by: Content type: ALL Problems Articles Games Stage: All Stage 1&2 Stage 2&3 Stage 3&4 Stage 4&5 Challenge level:
Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some. . . .
Complete the following expressions so that each one gives a four digit number as the product of two two digit numbers and uses the digits 1 to 8 once and only once.
What is the smallest number of answers you need to reveal in order to work out the missing headers?
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!?
The number 12 = 2^2 × 3 has 6 factors. What is the smallest natural number with exactly 36 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?
Find the highest power of 11 that will divide into 1000! exactly.
In this activity, the computer chooses a times table and shifts it. Can you work out the table and the shift each time?
I'm thinking of a number. When my number is divided by 5 the remainder is 4. When my number is divided by 3 the remainder is 2. Can you find my number?
Can you find a way to identify times tables after they have been shifted up?
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.
Twice a week I go swimming and swim the same number of lengths of the pool each time. As I swim, I count the lengths I've done so far, and make it into a fraction of the whole number of lengths. . . .
What is the remainder when 2^2002 is divided by 7? What happens with different powers of 2?
Explore the relationship between simple linear functions and their graphs.
This package contains a collection of problems from the NRICH website that could be suitable for students who have a good understanding of Factors and Multiples and who feel ready to take on some. . . .
Which pairs of cogs let the coloured tooth touch every tooth on the other cog? Which pairs do not let this happen? Why?
A game that tests your understanding of remainders.
How many zeros are there at the end of the number which is the product of first hundred positive integers?
Find some triples of whole numbers a, b and c such that a^2 + b^2 + c^2 is a multiple of 4. Is it necessarily the case that a, b and c must all be even? If so, can you explain why?
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...
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?
How many integers between 1 and 1200 are NOT multiples of any of the numbers 2, 3 or 5?
Make a line of green and a line of yellow rods so that the lines differ in length by one (a white rod)
Can you find any perfect numbers? Read this article to find out more...
The sum of the first 'n' natural numbers is a 3 digit number in which all the digits are the same. How many numbers have been summed?
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
The five digit number A679B, in base ten, is divisible by 72. What are the values of A and B?
Can you convince me of each of the following: If a square number is multiplied by a square number the product is ALWAYS a square number...
Using the digits 1, 2, 3, 4, 5, 6, 7 and 8, mulitply a two two digit numbers are multiplied to give a four digit number, so that the expression is correct. How many different solutions can you find?
A mathematician goes into a supermarket and buys four items. Using a calculator she multiplies the cost instead of adding them. How can her answer be the same as the total at the till?
Given the products of adjacent cells, can you complete this Sudoku?
What is the smallest number with exactly 14 divisors?
When the number x 1 x x x is multiplied by 417 this gives the answer 9 x x x 0 5 7. Find the missing digits, each of which is represented by an "x" .
Helen made the conjecture that "every multiple of six has more factors than the two numbers either side of it". Is this conjecture true?
A challenge that requires you to apply your knowledge of the properties of numbers. Can you fill all the squares on the board?
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?
Do you know a quick way to check if a number is a multiple of two? How about three, four or six?
What is the largest number which, when divided into 1905, 2587, 3951, 7020 and 8725 in turn, leaves the same remainder each time?
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.
A game in which players take it in turns to choose a number. Can you block your opponent?
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.
For this challenge, you'll need to play Got It! Can you explain the strategy for winning this game with any target?
Can you work out what size grid you need to read our secret message?
Follow this recipe for sieving numbers and see what interesting patterns emerge.
Can you find what the last two digits of the number $4^{1999}$ are?
Find the number which has 8 divisors, such that the product of the divisors is 331776.
What is the value of the digit A in the sum below: [3(230 + A)]^2 = 49280A
List any 3 numbers. It is always possible to find a subset of adjacent numbers that add up to a multiple of 3. Can you explain why and prove it?
Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?
Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?