A test consists of 20 questions, and students are asked to only answer 15 of them. In how many different ways can they choose 15 questions?

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asked Jan 26, 2017 57.9k views

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Unnati · Answer 1 · 2017-02-02T03:28:13+0000

n = 20, r = 15;
n C r = ( n * ( n - 1) ( n - 2 ) ... ( n - r + 1 )) / r ! =
20 C 15 = (20 * 19 * 18 * 17 ......8 * 7 * 6) / (15 * 14 * 13 ...* 5 * 4 * 3 * 2 * 1) =
= 15,504
Answer:
They can choose 15 questions in 15,504 ways.

A test consists of 20 questions, and students are asked to only answer 15 of them. In how many different ways can they choose 15 questions?

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