Take six coins: 5p, 10p, 20p, 50p, £1, £2.
Put five of them in a row using these clues:
The total of the first three coins is £1.25 The total of the last three coins is £2.70. The last coin is half the value of the first coin.
You could time how long it takes you to solve it and compare your time with your friends!
Come and see me with your answer.