Solve the problem.
-Mary finds 10 fish at a pet store that she would like to buy, but she can afford only 4 of them. In how many ways can she make her selection? How many ways can she make her selection if he decides that one of the fish
Is a must?
A) 210; 84
B) 151,200; 60,480
C) 5040; 504
D) 2520; 252

Question

Quizplus · Accepted Answer

The number of ways Mary can select 4 fish out of 10 is calculated using combinations since the order of selection does not matter. This is given by 10C4 = 10! / (4!(10-4)!) = 210 ways. If one fish is a must, then she only needs to choose 3 out of the remaining 9, which is 9C3 = 9! / (3!(9-3)!) = 84 ways.

Solve the Problem. -Mary Finds 10 Fish at a Pet Store That She