Working systematically

article
Impuzzable

This is about a fiendishly difficult jigsaw and how to solve it using a computer program.
interactivity
Introducing NRICH TWILGO

Age

5 to 18

Challenge level

We're excited about this new program for drawing beautiful mathematical designs. Can you work out how we made our first few pictures and, even better, share your most elegant solutions with us?
game
Favourite

The remainders game

Age

7 to 14

Challenge level

Play this game and see if you can figure out the computer's chosen number.
game

Twinkle twinkle

Age

7 to 14

Challenge level

A game for 2 people. Take turns placing a counter on the star. You win when you have completed a line of 3 in your colour.
problem
Central sum

Age

11 to 14

Challenge level

Can you find numbers between 100 and 999 that have a middle digit equal to the sum of the other two digits?
problem
Birthday cake candles

Age

7 to 11

Challenge level

This challenge involves calculating the number of candles needed on birthday cakes. It is an opportunity to explore numbers and discover new things.
problem
Pocket money

Age

11 to 14

Challenge level

Which of these pocket money systems would you rather have?
problem
Price match

Age

7 to 11

Challenge level

Can you find pairs of differently sized windows that cost the same?
problem
Almost one

Age

11 to 14

Challenge level

Choose some fractions and add them together. Can you get close to 1?
problem
Jigsaw pieces

Age

7 to 11

Challenge level

How will you go about finding all the jigsaw pieces that have one peg and one hole?