Question

Four students can choose to participate in a charity event either on Saturday or Sunday. What’s the probability that there is at least one student at both Saturday's and Sunday's events?A) 1/8B) 3/8C) 5/8D) 7/8

Answer 1

D) 7/8

Explanation:

The probability that there is at least one student at both Saturday's and Sunday's events is the inverse of the probability of having all students selecting either Saturday OR Sunday.

Since the probability of a student selecting Saturday is 0.5, the probability of all 4 students selecting that day is

0.5 * 0.5 * 0.5 * 0.5 = 1/16

Then the probability of having all students selecting either Saturday OR Sunday is twice that, which is 2/16, or 1/8

Therefore the probability that there is at least one student at both Saturday's and Sunday's events is 1 - 1/8 = 8/8 - 1/8 = 7/8