Eight volunteers offer to help at a blood-donation camp, and the organiser needs a group of 3 of them. The 3 have identical duties. How many different groups can be chosen?

11Correct answerYour answer24Correct answerYour answer56Correct answerYour answer336Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

Order does not matter, so this is a combination.
${}^{8}C_{3} = \frac{8 \times 7 \times 6}{3 \times 2 \times 1} = \frac{336}{6} = 56$ .

Worth noting

336 is ${}^{8}P_{3}$ , which counts the same three people 6 times over, once for each order. 24 is $8 \times 3$ .

Ten questions from Counting and Basic Probability, at your own pace.

Ten questions from Counting and Basic Probability, at your own pace.

Explanation