3 × 10 3 \times10

How many ways are there to elect a team of three students out of a class of 30?

The answer is 4060.

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1 solution

Arpit MIshra
Apr 8, 2015

The first student can be chosen in 30 ways, the second in 29 ways and the third on 28 ways. Thus we have 30 × 29 × 28 30 \times 29 \times 28 ways.

However, each team was counted several times: the same trio of students can be chosen in different ways.

For instance, choosing student A first, then student B, and finally, C is the same as choosing C first, then A, and then B. Since the number of permutations of 3 elements is 3!, each team was counted exactly 3!=6 times.

Therefore the answer is 30 × 29 × 28 3 ! \frac {30 \times 29 \times 28}{3!} .

= 4060 . \boxed{4060}.

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