Working backwards can be a very useful problem-solving skill. These activities lend themselves to being tackled in this way.

This collection is one of our Primary Curriculum collections - tasks that are grouped by topic.

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### Nim-7

Can you work out how to win this game of Nim? Does it matter if you go first or second?

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### Junior Frogs

Have a go at this well-known challenge. Can you swap the frogs and toads in as few slides and jumps as possible?

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### What's in the Box?

This big box multiplies anything that goes inside it by the same number. If you know the numbers that come out, what multiplication might be going on in the box?

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### First Connect Three

Add or subtract the two numbers on the spinners and try to complete a row of three. Are there some numbers that are good to aim for?

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### Nice or Nasty

There are nasty versions of this dice game but we'll start with the nice ones...

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### Missing Multipliers

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

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### Play to 37

In this game for two players, the idea is to take it in turns to choose 1, 3, 5 or 7. The winner is the first to make the total 37.

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### Would You Rather?

Would you rather: Have 10% of Â£5 or 75% of 80p? Be given 60% of 2 pizzas or 26% of 5 pizzas?

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### Multiplication Squares

Can you work out the arrangement of the digits in the square so that the given products are correct? The numbers 1 - 9 may be used once and once only.

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### Maze 100

Can you go through this maze so that the numbers you pass add to exactly 100?

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### Mystery Matrix

Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.

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### All the Digits

This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?

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### Got It

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.

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### Andy's Marbles

Andy had a big bag of marbles but unfortunately the bottom of it split and all the marbles spilled out. Use the information to find out how many there were in the bag originally.

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### Counting Cards

A magician took a suit of thirteen cards and held them in his hand
face down. Every card he revealed had the same value as the one he
had just finished spelling. How did this work?