Question

Of all the Sunny Club members in a particular city, 25% prefer swimming on weekends and 75% prefer swimming on weekdays. 10% of the members in the city prefer swimming on weekends and are female. 55% of the members in the city prefer swimming on weekdays and are female. What is the probability that a randomly selected club member is female, given that the person prefers swimming on weekends? (A).19, (B).20, (C).24, (D).40, (E).55

Answer 1

The easiest way to solve this problem is to make a table, based on 100 total person

Prefer week ends Prefer week days Total

Female 10 55 65

Male 15 20 35

Total 25 75 100

The bold numbers are conclusions. The plain numbers are data.

The probability that a randomly selected club member is female, given that that person prefers swimming on weekends is [10 / 25] = 0.40

Answer: option D. 0.40