Ben has five coins in his pocket. How much money might he have?
Vera is shopping at a market with these coins in her purse. Which
things could she give exactly the right amount for?
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?
If I pay the exact fare, the smallest number of coins I could use is 4 (2 x 20p and 2 x 2p). If I receive change, then it is not possible for only 2 coins to change hands since this would involve my giving the driver one coin (50p, £1 or £2) and receiving only one coin in change, but the necessary coin does not exist. However, if I give the driver a 50p coin and receive a 5p coin and a 1p coin in
change, then only 3 coins change hands.
This problem is taken from the UKMT Mathematical Challenges.