Question

For a certain class, the following data table compares how many students have a brother or a sister. What is the probability that a randomly chosen student from the class has a brother and a sister?
Has a brother Does not have a brother
Has a sister 7 2
Does not have a sister 3 8

Answer 1

There are 7 students who have both a brother and a sister, out of a total of 7+2+3+8 = 20 students.

Probability = 7/20 = 0.35 = 35%.