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How many ways can you find to put in operation signs (+ - x Ã·) to make 100?

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This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.

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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?

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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" .

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The number 10112359550561797752808988764044943820224719 is called a 'slippy number' because, when the last digit 9 is moved to the front, the new number produced is the slippy number multiplied by 9.

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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. . . .

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When I type a sequence of letters my calculator gives the product of all the numbers in the corresponding memories. What numbers should I store so that when I type 'ONE' it returns 1, and when I type. . . .

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Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.

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These pictures and answers leave the viewer with the problem "What is the Question". Can you give the question and how the answer follows?

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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?

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Use your logical reasoning to work out how many cows and how many sheep there are in each field.

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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. . . .

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Can you find different ways of creating paths using these paving slabs?

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What is the largest number you can make using the three digits 2, 3 and 4 in any way you like, using any operations you like? You can only use each digit once.

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What is the smallest number of answers you need to reveal in order to work out the missing headers?

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Skippy and Anna are locked in a room in a large castle. The key to that room, and all the other rooms, is a number. The numbers are locked away in a problem. Can you help them to get out?

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Amy has a box containing domino pieces but she does not think it is a complete set. Which of her domino pieces are missing?

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Each clue in this Sudoku is the product of the two numbers in adjacent cells.

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Play this game and see if you can figure out the computer's chosen number.

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Choose any four consecutive even numbers. Multiply the two middle numbers together. Multiply the first and last numbers. Now subtract your second answer from the first. Try it with your own. . . .

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Mathematicians are always looking for efficient methods for solving problems. How efficient can you be?

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

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The clues for this Sudoku are the product of the numbers in adjacent squares.

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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. . . .

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If you take a three by three square on a 1-10 addition square and multiply the diagonally opposite numbers together, what is the difference between these products. Why?

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Look at what happens when you take a number, square it and subtract your answer. What kind of number do you get? Can you prove it?

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Given the products of adjacent cells, can you complete this Sudoku?

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I'm thinking of a number. My number is both a multiple of 5 and a multiple of 6. What could my number be?

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Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?

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This task combines spatial awareness with addition and multiplication.

In this article, Alf outlines six activities using the Gattegno chart, which help to develop understanding of place value, multiplication and division.

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Using the digits 1 to 9, the number 4396 can be written as the product of two numbers. Can you find the factors?

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This Sudoku requires you to do some working backwards before working forwards.

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This challenge combines addition, multiplication, perseverance and even proof.

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In this simulation of a balance, you can drag numbers and parts of number sentences on to the trays. Have a play!

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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.

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Find the number which has 8 divisors, such that the product of the divisors is 331776.

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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?

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The number 12 = 2^2 × 3 has 6 factors. What is the smallest natural number with exactly 36 factors?

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A game for 2 or more players with a pack of cards. Practise your skills of addition, subtraction, multiplication and division to hit the target score.

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Here is a picnic that Petros and Michael are going to share equally. Can you tell us what each of them will have?

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A game for 2 people. Use your skills of addition, subtraction, multiplication and division to blast the asteroids.

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A game for 2 people using a pack of cards Turn over 2 cards and try to make an odd number or a multiple of 3.

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Benâ€™s class were cutting up number tracks. First they cut them into twos and added up the numbers on each piece. What patterns could they see?

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Your vessel, the Starship Diophantus, has become damaged in deep space. Can you use your knowledge of times tables and some lightning reflexes to survive?

This article for teachers looks at how teachers can use problems from the NRICH site to help them teach division.

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The Scot, John Napier, invented these strips about 400 years ago to help calculate multiplication and division. Can you work out how to use Napier's bones to find the answer to these multiplications?

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Here are the prices for 1st and 2nd class mail within the UK. You have an unlimited number of each of these stamps. Which stamps would you need to post a parcel weighing 825g?