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

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BTGmoderatorDC: Moderator; Posts: 7187; Joined: Thu Sep 07, 2017 4:43 pmFollowed by: 23 members

by BTGmoderatorDC » Tue Feb 21, 2023 5:18 pm

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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

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Source: Beat The GMAT — Problem Solving | Tue Feb 21, 2023 5:18 pm

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

by Scott@TargetTestPrep » Wed Mar 08, 2023 11:42 am

BTGmoderatorDC wrote: ↑
Tue Feb 21, 2023 5:18 pm
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

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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