math
posted by October .
A group of friends took a bus trip. Each traveler gave the bus driver a tip using the same nine coins. The total tip was $8.41. How many nickels did the driver receive?

How many friends made the trip? In this case we can decide by loking for intger factors of 841. It cannot be a prime number if the tips were the same..
If each person gave the same tip, there must have been 29 of them, because that is the only integer factor of 841. The tip would be 0.29 per passenger.
Five nickels and 4 pennies can form 29 cents. That is the only way to do it with nine coins.
Therefore the bus driver ends up with 29x5 = 145 nickels.