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There are 80 NRICH Mathematical resources connected to Addition and subtraction, you may find related items under Calculations and numerical methods.
Broad Topics > Calculations and numerical methods > Addition and subtractionIn each of these games, you will need a little bit of luck, and your knowledge of place value to develop a winning strategy.
Can you use the clues to complete these 5 by 5 Mathematical Sudokus?
Can you use the clues to complete these 4 by 4 Mathematical Sudokus?
How many ways can you find to put in operation signs (+, −, ×, ÷) to make 100?
What happens when you add a three digit number to its reverse?
By selecting digits for an addition grid, what targets can you make?
Try out some calculations. Are you surprised by the results?
This article suggests some ways of making sense of calculations involving positive and negative numbers.
Play this game to learn about adding and subtracting positive and negative numbers
Imagine a very strange bank account where you are only allowed to do two things...
Take three consecutive numbers and add them together. What do you notice?
Charlie has made a Magic V. Can you use his example to make some more? And how about Magic Ls, Ns and Ws?
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.
Crosses can be drawn on number grids of various sizes. What do you notice when you add opposite ends?
Different combinations of the weights available allow you to make different totals. Which totals can you make?
How can we help students make sense of addition and subtraction of negative numbers?
Do you notice anything about the solutions when you add and/or subtract consecutive negative numbers?
In this game the winner is the first to complete a row of three. Are some squares easier to land on than others?
Use the differences to find the solution to this Sudoku.
Delight your friends with this cunning trick! Can you explain how it works?
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?
Can you arrange these numbers into 7 subsets, each of three numbers, so that when the numbers in each are added together, they make seven consecutive numbers?
Try entering different sets of numbers in the number pyramids. How does the total at the top change?
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.
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.
We start with one yellow cube and build around it to make a 3x3x3 cube with red cubes. Then we build around that red cube with blue cubes and so on. How many cubes of each colour have we used?
Can you find six numbers to go in the Daisy from which you can make all the numbers from 1 to a number bigger than 25?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
15 = 7 + 8 and 10 = 1 + 2 + 3 + 4. Can you say which numbers can be expressed as the sum of two or more consecutive integers?
Can you explain the strategy for winning this game with any target?
Three children are going to buy some plants for their birthdays. They will plant them within circular paths. How could they do this?
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Ann thought of 5 numbers and told Bob all the sums that could be made by adding the numbers in pairs. The list of sums is 6, 7, 8, 8, 9, 9, 10,10, 11, 12. Help Bob to find out which numbers Ann was thinking of.
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 'TWO' it returns 2, and so on.
This challenge is to make up YOUR OWN alphanumeric. Each letter represents a digit and where the same letter appears more than once it must represent the same digit each time.
There are exactly 3 ways to add 4 odd numbers to get 10. Find all the ways of adding 8 odd numbers to get 20. To be sure of getting all the solutions you will need to be systematic. What about a total of 15 with 6 odd numbers?
Using the 8 dominoes make a square where each of the columns and rows adds up to 8
A combination mechanism for a safe comprises thirty-two tumblers numbered from one to thirty-two in such a way that the numbers in each wheel total 132... Could you open the safe?
Find the values of the nine letters in the sum: FOOT + BALL = GAME
What is the sum of all the digits in all the integers from one to one million?
Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?
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. Try lots of examples. What happens? Can you explain it?
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 other possibilities for yourself!
Choose any three by three square of dates on a calendar page...