There are **255** NRICH Mathematical resources connected to **Addition & subtraction**, you may find related items under Calculations and Numerical Methods.

Try out this number trick. What happens with different starting numbers? What do you notice?

Are these statements relating to calculation and properties of shapes always true, sometimes true or never true?

Try out some calculations. Are you surprised by the results?

Throw the dice and decide whether to double or halve the number. Will you be the first to reach the target?

Use five steps to count forwards or backwards in 1s or 10s to get to 50. What strategies did you use?

This article suggests some ways of making sense of calculations involving positive and negative numbers.

What happens when you add three numbers together? Will your answer be odd or even? How do you know?

This investigates one particular property of number by looking closely at an example of adding two odd numbers together.

Dotty Six is a simple dice game that you can adapt in many ways.

Tom and Ben visited Numberland. Use the maps to work out the number of points each of their routes scores.

Two children made up a game as they walked along the garden paths. Can you find out their scores? Can you find some paths of your own?

If you have ten counters numbered 1 to 10, how many can you put into pairs that add to 10? Which ones do you have to leave out? Why?

What happens when you add the digits of a number then multiply the result by 2 and you keep doing this? You could try for different numbers and different rules.

This group activity will encourage you to share calculation strategies and to think about which strategy might be the most efficient.

This activity is best done with a whole class or in a large group. Can you match the cards? What happens when you add pairs of the numbers together?

Can you each work out the number on your card? What do you notice? How could you sort the cards?

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

Here is a chance to play a version of the classic Countdown Game.

Can you put the numbers 1-5 in the V shape so that both 'arms' have the same total?

Crosses can be drawn on number grids of various sizes. What do you notice when you add opposite ends?

A group of children are using measuring cylinders but they lose the labels. Can you help relabel them?

Different combinations of the weights available allow you to make different totals. Which totals can you make?

Use your logical-thinking skills to deduce how much Dan's crisps and ice-cream cost altogether.

How can we help students make sense of addition and subtraction of negative numbers?

The picture shows a lighthouse and many underwater creatures. If you know the markings on the lighthouse are 1m apart, can you work out the distances between some of the different creatures?

In this game, you can add, subtract, multiply or divide the numbers on the dice. Which will you do so that you get to the end of the number line first?

Can you use the numbers on the dice to reach your end of the number line before your partner beats you?

Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?

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?

In this game the winner is the first to complete a row of three. Are some squares easier to land on than others?

These caterpillars have 16 parts. What different shapes do they make if each part lies in the small squares of a 4 by 4 square?

Ahmed is making rods using different numbers of cubes. Which rod is twice the length of his first rod?

Delight your friends with this cunning trick! Can you explain how it works?

Have a go at this game which involves throwing two dice and adding their totals. Where should you place your counters to be more likely to win?

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?

Place the numbers from 1 to 9 in the squares below so that the difference between joined squares is odd. How many different ways can you do this?

Choose four of the numbers from 1 to 9 to put in the squares so that the differences between joined squares are odd.

These sixteen children are standing in four lines of four, one behind the other. They are each holding a card with a number on it. Can you work out the missing numbers?

Use these head, body and leg pieces to make Robot Monsters which are different heights.

Try entering different sets of numbers in the number pyramids. How does the total at the top change?

There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?

Find out what a Deca Tree is and then work out how many leaves there will be after the woodcutter has cut off a trunk, a branch, a twig and a leaf.

Can you put the numbers 1 to 8 into the circles so that the four calculations are correct?

A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly £100 if the prices are £10 for adults, 50p for pensioners and 10p for children.

Arrange three 1s, three 2s and three 3s in this square so that every row, column and diagonal adds to the same total.