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What is the probability of getting only one head in a single throw

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What is the probability of getting only one head in a single throw [#permalink]

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New post Updated on: 14 Sep 2014, 21:56
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Question Stats:

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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




Source: 4gmat

How do we solve such problems?

Originally posted by alphonsa on 14 Sep 2014, 08:14.
Last edited by alphonsa on 14 Sep 2014, 21:56, edited 2 times in total.
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Concentration: Operations, General Management
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Re: What is the probability of getting only one head in a single throw [#permalink]

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New post 14 Sep 2014, 09:40
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alphonsa wrote:
What is the probability of getting a head in a single throw of three fair coins?

A) 1/2
B) 3/8
C) 1/4
D) 1/5
E) 5/8




Source: 4gmat

How do we solve such problems?



I'm a bit confused with the wording in the question and the answer choices. I was wondering if you meant probability of getting only 1 head.

According to the way the question is answer should be 7/8
If the question is of getting only one head then answer is 3/8

Explanation

Probability of an event = No. of ways in which event occurs / Total number of outcomes possible

On tossing three coins the total number of outcomes possible are

HHH
HHT
HTH
THH
HTT
THT
TTH
TTT

So there are 8 possible outcomes. Now to find the probability of desired outcomes.

Case I :
Probability of getting a head ( Can be only 1 head, 2 Heads or 3 Heads)

HHH
HHT
HTH
THH
HTT
THT
TTH

So 7 ways in which event occurs out of 8 possible outcomes. Hence probability = 7/8


Case II:
Probability of getting "ONLY" one head

HTT
THT
TTH

So 3 ways in which event occurs out of 8 possible outcomes. Hence probability = 3/8

I guess your question should have been to find the probability of getting ONLY one head, then the answer is B
Current Student
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Joined: 22 Jul 2014
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Concentration: General Management, Finance
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Re: What is the probability of getting only one head in a single throw [#permalink]

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New post 14 Sep 2014, 21:57
Thanks. I had posted the question the way it had been worded in the book


However to avoid confusion, I have edited it here
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Re: What is the probability of getting only one head in a single throw [#permalink]

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New post 09 Feb 2018, 11:09
alphonsa 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



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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Re: What is the probability of getting only one head in a single throw   [#permalink] 09 Feb 2018, 11:09
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What is the probability of getting only one head in a single throw

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