ACT Math · Probability and counting

In a race with 5 runners, in how many different ways can 1st, 2nd, and 3rd place be awarded?

In a race with 5 runners, in how many different ways can 1st, 2nd, and 3rd place be awarded?

Answer and explanation

Answer: H: 60

The order matters because 1st, 2nd, and 3rd place are different awards. There are 55 choices for first place, then 44 for second, then 33 for third, so the total is 5⋅4⋅3=605\cdot4\cdot3=60, choice H. This is the permutation P(5,3)P(5,3). Choice F (1010) is the combination C(5,3)C(5,3), which counts groups of three runners without regard to order. Choice G (1515) is 5⋅35\cdot3, which uses only two of the three positions. Choice J (125125) is 535^3, which would let the same runner win all three places.

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