10 year retrospective - January 2007, All Stages

Problems

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Domino Sorting

Stage: 1 Challenge Level: Challenge Level:1

Try grouping the dominoes in the ways described. Are there any left over each time? Can you explain why?

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Overlapping Squares

Stage: 2 Challenge Level: Challenge Level:1

Have a good look at these images. Can you describe what is happening? There are plenty more images like this on NRICH's Exploring Squares CD.

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Consecutive Numbers

Stage: 2 Challenge Level: Challenge Level:1

An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

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One to Fifteen

Stage: 2 Challenge Level: Challenge Level:1

Can you put the numbers from 1 to 15 on the circles so that no consecutive numbers lie anywhere along a continuous straight line?

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Square Tangram

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

This was a problem for our birthday website. Can you use four of these pieces to form a square? How about making a square with all five pieces?

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Magic Matrix

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

Find out why these matrices are magic. Can you work out how they were made? Can you make your own Magic Matrix?

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It's a Tie

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

Kaia is sure that her father has worn a particular tie twice a week in at least five of the last ten weeks, but her father disagrees. Who do you think is right?

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Isosceles Triangles

Stage: 3 Challenge Level: Challenge Level:1

Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?

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Triangles to Tetrahedra

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

Starting with four different triangles, imagine you have an unlimited number of each type. How many different tetrahedra can you make? Convince us you have found them all.

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Noughts and Crosses

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

Ever thought of playing three dimensional Noughts and Crosses? This problem might help you visualise what's involved.

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More Number Pyramids

Stage: 3 and 4 Challenge Level: Challenge Level:2 Challenge Level:2

When number pyramids have a sequence on the bottom layer, some interesting patterns emerge...

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Big Powers

Stage: 3 and 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.

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One Basket or Group Photo

Stage: 2, 3, 4 and 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Libby Jared helped to set up NRICH and this is one of her favourite problems. It's a problem suitable for a wide age range and best tackled practically.

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Nine Colours

Stage: 3 and 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

You have 27 small cubes, 3 each of nine colours. Use the small cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of every colour.

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Fac-finding

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

Lyndon chose this as one of his favourite problems. It is accessible but needs some careful analysis of what is included and what is not. A systematic approach is really helpful.

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Three by One

Stage: 5 Challenge Level: Challenge Level:1

There are many different methods to solve this geometrical problem - how many can you find?

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All about Ratios

Stage: 5 Challenge Level: Challenge Level:1

A new problem posed by Lyndon Baker who has devised many NRICH problems over the years.

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Gold Yet Again

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Nick Lord says "This problem encapsulates for me the best features of the NRICH collection."