Three interpreters and six tourists are randomly divided into three groups of three people each. What is the probability that each group contains an interpreter?Total outcomes:Three groups of three people each.
So, we have the following:
\(\frac{\frac{9 ⋅ 8 ⋅ 7}{3!} × \frac{6 ⋅ 5 ⋅ 4}{3!} × \frac{3 ⋅ 2 ⋅ 1}{3!}}{3!}\)
Dividing everything by 3! is necessary because the groups are indistinguishable. So, the order of the groups doesn't matter.
Favorable outcomes:First assign the interpreters to three groups:
\(I\) _ _ \(I\) _ _ \(I\) _ _
Then, assign the six tourists to the interpreters:
\(I\) \(\frac{6 ⋅ 5}{2!}\) \(I\) \(\frac{4 ⋅ 3}{2!}\) \(I\) \(\frac{2 ⋅ 1}{2!}\)
So, the number of favorable outcomes is \(\frac{6!}{2!2!2!}\)
Favorable over total:
\(\frac{\frac{6!}{2!2!2!}}{\frac{\frac{9 ⋅ 8 ⋅ 7}{3!} × \frac{6 ⋅ 5 ⋅ 4}{3!} × \frac{3 ⋅ 2 ⋅ 1}{3!}}{3!}} = \frac{9}{28}\)
(A) \(\frac{1}{10}\)
(B) \(\frac{2}{9}\)
(C) \(\frac{1}{3}\)
(D) \(\frac{2}{7}\)
(E) \(\frac{9}{28}\)Correct answer: E