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What is the probability of getting only 1 head in a single

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by GMATGuruNY » Mon Jul 30, 2018 1:31 am
BTGmoderatorDC wrote:What is the probability of getting only 1 head in a single throw of three fair coins?

A) 1/2
B) 3/8
C) 1/4
D) 1/5
E) 5/8
P(HTT) = 1/2 * 1/2 * 1/2 = 1/8.
Since a good outcome will be yielded if H is first, second or third, we multiply by 3:
1/8 * 3 = 3/8.

The correct answer is B.
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by deloitte247 » Wed Aug 01, 2018 3:17 pm
$$\Probability\ of\ an\ event\ =\ \frac{Occurence}{Possible\ outcome}$$
On tossing 3 fair coins, we have 8 possible outcome.
H H H
H H T
H T H
H T T
T H T
T H H
T T H
T T T

The desired outcome with only one head occurring is just 3.
H T T
T H T
T T H
$$The\ probability\ of\ having\ one\ head\ occurring\ out\ of\ all\ the\ possible\ outcome\ is\ just\ \frac{3}{8}$$
Option B is the correct answer.
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by Jeff@TargetTestPrep » Sat Aug 18, 2018 7:00 pm
BTGmoderatorDC wrote:What is the probability of getting only 1 head in a single throw of three fair coins?

A) 1/2
B) 3/8
C) 1/4
D) 1/5
E) 5/8
First, we need to determine the probability of H-T-T = 1/2 x 1/2 x 1/2 = 1/8.

Since H-T-T can be arranged in 3!/2! = 3 ways, the total probability is 3/8.

Answer: B

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