posted by Shawn .
selecting three (3) coins, but assume that there are 5 dimes, 4 nickels, and 2 quarters.
In how many possible ways can the selection be made so that the value of the coins is at least 25 cents?
The only possible cases are, hope I did not miss any
DDD - 30
DDN - 25
DDQ - 45
DNN - 20
DNQ - 40
DQQ - 60
NNN - 15
NNQ - 35
NQQ - 55
How many of these amount to at least 25 cents?
(notice that the fact that we have 5 dimes and 4 nickels is of no consequence, since we can use at most 3, but the 2 quarters limits the cases)