John tossed a fair coin 3 times. What is the probability that the outcome was “tails” exactly twice?

[BTGmoderatorDC]

John tossed a fair coin 3 times. What is the probability that the outcome was “tails” exactly twice?

A. 1/8
B. 1/4
C. 3/8
D. 1/2
E. 9/10


OA C

Source: EMPOWERgmat

[Scott@TargetTestPrep]

John tossed a fair coin 3 times. What is the probability that the outcome was “tails” exactly twice?

A. 1/8
B. 1/4
C. 3/8
D. 1/2
E. 9/10


OA C

Source: EMPOWERgmat

We need to determine the following:

P(TTH) = (1/2)^3 = 1/8

Since TTH can be arranged in 3!/2! = 3 ways, the probability is 3 x (1/8) = 3/8.

Answer: C