Money problem
Probability
Level
3
There are 5 types of coins in a certain country. They worth 1, 8, 32, 80, 350. How many coins are required so you can pay any amount of money under 2000 and have 6 coins left?
The answer is 23.
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1 solution
Try thinking what will happen if you need to pay any amount of coins under 32. You will need at least 7 coins that worth 1, 3 coins that worth 8, Since 7 add 3 times 8 equals 31. Keep thinking in this direction, and you will need 21 coins. But however, you need to have at least 6 coins left after any payment. The payment that uses the most money is 1989, you need 17 coins. Therefore you need a total of 23 coins.