Currency Exchange
Dan has nine 20p coins and his sister Ann has eight 50p coins. What is the smallest number of coins that must change hands so that Dan and Ann end up with equal amounts of money?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
You may also like
Oh for the Mathematics of Yesteryear
A garrison of 600 men has just enough bread ... but, with the news that the enemy was planning an attack... How many ounces of bread a day must each man in the garrison be allowed, to hold out 45 days against the siege of the enemy?
Thirty Nine, Seventy Five
We have exactly 100 coins. There are five different values of coins. We have decided to buy a piece of computer software for 39.75. We have the correct money, not a penny more, not a penny less! Can you discover what the five different types of coins are worth and how many of each we have saved?
History of Money
If you would like a new CD you would probably go into a shop and buy one using coins or notes. (You might need to do a bit of saving first!) However, this way of paying for the things you want did not always exist. Find out more ...