Question

In a class of 25 students, 13 have a brother and 9 have a sister. There are 7 students who do not have any siblings. What is the probability that a student chosen randomly from the class has a brother and a sister?

Answer 1

Explanation:

Discussion

9 with a sister

13 with a brother

7 with neither.

The total is 29 so you are counting some siblings twice. There are 29 - 25 students that have both, so 4 students have both.

P(brother and sister) = 4/25

P(brother and sister) = 0.16

Answer

P = 0.16