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Resources tagged with Addition & subtraction similar to Cracking Codes:

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Broad Topics > Calculations and Numerical Methods > Addition & subtraction

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Become Maths Detectives

Stage: 2 Challenge Level: Challenge Level:1

Explore Alex's number plumber. What questions would you like to ask? Don't forget to keep visiting NRICH projects site for the latest developments and questions.

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How Many?

Stage: 1 Challenge Level: Challenge Level:1

This project challenges you to work out the number of cubes hidden under a cloth. What questions would you like to ask?

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It Was 2010!

Stage: 1 and 2 Challenge Level: Challenge Level:1

If the answer's 2010, what could the question be?

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A Dotty Problem

Stage: 2 Challenge Level: Challenge Level:1

Starting with the number 180, take away 9 again and again, joining up the dots as you go. Watch out - don't join all the dots!

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Follow the Numbers

Stage: 2 Challenge Level: Challenge Level:1

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.

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Pairs of Numbers

Stage: 1 Challenge Level: Challenge Level:1

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?

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Exploring Number Patterns You Make

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Explore Alex's number plumber. What questions would you like to ask? What do you think is happening to the numbers?

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Sept03 Sept03 Sept03

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

This number has 903 digits. What is the sum of all 903 digits?

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Making Maths: Double-sided Magic Square

Stage: 2 and 3 Challenge Level: Challenge Level:2 Challenge Level:2

Make your own double-sided magic square. But can you complete both sides once you've made the pieces?

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All Seated

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Look carefully at the numbers. What do you notice? Can you make another square using the numbers 1 to 16, that displays the same properties?

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Numbers Numbers Everywhere!

Stage: 1 and 2

Bernard Bagnall recommends some primary school problems which use numbers from the environment around us, from clocks to house numbers.

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Got it Article

Stage: 2 and 3

This article gives you a few ideas for understanding the Got It! game and how you might find a winning strategy.

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Caterpillars

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

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?

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Abundant Numbers

Stage: 2 Challenge Level: Challenge Level:1

48 is called an abundant number because it is less than the sum of its factors (without itself). Can you find some more abundant numbers?

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Month Mania

Stage: 1 and 2 Challenge Level: Challenge Level:2 Challenge Level:2

Can you design a new shape for the twenty-eight squares and arrange the numbers in a logical way? What patterns do you notice?

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Neighbours

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

In a square in which the houses are evenly spaced, numbers 3 and 10 are opposite each other. What is the smallest and what is the largest possible number of houses in the square?

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Escape from the Castle

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

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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Sort Them Out (2)

Stage: 2 Challenge Level: Challenge Level:1

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

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Homes

Stage: 1 Challenge Level: Challenge Level:1

There are to be 6 homes built on a new development site. They could be semi-detached, detached or terraced houses. How many different combinations of these can you find?

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Sometimes We Lose Things

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Well now, what would happen if we lost all the nines in our number system? Have a go at writing the numbers out in this way and have a look at the multiplications table.

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Magic Constants

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

In a Magic Square all the rows, columns and diagonals add to the 'Magic Constant'. How would you change the magic constant of this square?

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Scoring with Dice

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

I throw three dice and get 5, 3 and 2. Add the scores on the three dice. What do you get? Now multiply the scores. What do you notice?

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Cuisenaire Environment

Stage: 1 and 2 Challenge Level: Challenge Level:1

An environment which simulates working with Cuisenaire rods.

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Magic Triangle

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Place the digits 1 to 9 into the circles so that each side of the triangle adds to the same total.

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Making Longer, Making Shorter

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

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

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One Wasn't Square

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Mrs Morgan, the class's teacher, pinned numbers onto the backs of three children. Use the information to find out what the three numbers were.

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Napier's Bones

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

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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Street Sequences

Stage: 1 and 2 Challenge Level: Challenge Level:1

Investigate what happens when you add house numbers along a street in different ways.

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Penta Post

Stage: 2 Challenge Level: Challenge Level:1

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?

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How Much Did it Cost?

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

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

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Odds and Threes

Stage: 2 Challenge Level: Challenge Level:1

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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Asteroid Blast

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

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

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Ring a Ring of Numbers

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

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

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Number Tracks

Stage: 2 Challenge Level: Challenge Level:1

Ben’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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Pouring the Punch Drink

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

There are 4 jugs which hold 9 litres, 7 litres, 4 litres and 2 litres. Find a way to pour 9 litres of drink from one jug to another until you are left with exactly 3 litres in three of the jugs.

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Brothers and Sisters

Stage: 2 Challenge Level: Challenge Level:1

Cassandra, David and Lachlan are brothers and sisters. They range in age between 1 year and 14 years. Can you figure out their exact ages from the clues?

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Numbered Cars

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

I was looking at the number plate of a car parked outside. Using my special code S208VBJ adds to 65. Can you crack my code and use it to find out what both of these number plates add up to?

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Eggs in Baskets

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

There are three baskets, a brown one, a red one and a pink one, holding a total of 10 eggs. Can you use the information given to find out how many eggs are in each basket?

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The Pied Piper of Hamelin

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

This problem is based on the story of the Pied Piper of Hamelin. Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!

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Bean Bags for Bernard's Bag

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

How could you put eight beanbags in the hoops so that there are four in the blue hoop, five in the red and six in the yellow? Can you find all the ways of doing this?

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Make 100

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Find at least one way to put in some operation signs (+ - x ÷) to make these digits come to 100.

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Number Round Up

Stage: 1 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Arrange the numbers 1 to 6 in each set of circles below. The sum of each side of the triangle should equal the number in its centre.

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Buying a Balloon

Stage: 2 Challenge Level: Challenge Level:1

Lolla bought a balloon at the circus. She gave the clown six coins to pay for it. What could Lolla have paid for the balloon?

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Mrs Beeswax

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

In how many ways could Mrs Beeswax put ten coins into her three puddings so that each pudding ended up with at least two coins?

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Super Shapes

Stage: 2 Short Challenge Level: Challenge Level:1

The value of the circle changes in each of the following problems. Can you discover its value in each problem?

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Twenty Divided Into Six

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Katie had a pack of 20 cards numbered from 1 to 20. She arranged the cards into 6 unequal piles where each pile added to the same total. What was the total and how could this be done?

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Spiders and Flies

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

There were 22 legs creeping across the web. How many flies? How many spiders?

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A Mixed-up Clock

Stage: 2 Challenge Level: Challenge Level:1

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?

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Zargon Glasses

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families?

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The Puzzling Sweet Shop

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

There were chews for 2p, mini eggs for 3p, Chocko bars for 5p and lollypops for 7p in the sweet shop. What could each of the children buy with their money?