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
The OA is the option B.
How can I determine the correct answer? Shouldn't it be (1/2)^3=1/8? I am confused.<i class="em em-confused"></i>
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What is the probability of getting only 1 head in a single
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EconomistGMATTutor
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Hi M7MBA.M7MBA 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
The OA is the option B.
How can I determine the correct answer? Shouldn't it be (1/2)^3=1/8? I am confused.<i class="em em-confused"></i>
Let's take a look at your question.
First, we have _ _ _ (3) places, and each place has 2 possibilities (H or T). Hence, there are a total of 2*2*2=8 possibilities.
Now, we want to obtain ONLY one head, this implies that we have the next cases:
HTT
THT
TTH
Therefore, there are 3 cases.
Finally, the answer is cases favorable / total of cases = 3/8. This is why the correct answer is B.
I hope this answer may help you.
Feel free to ask me again if you have any doubt.
Regards.
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Hi M7MBA,
Since we're tossing just 3 coins, there aren't that many possible outcomes. This question can be solved simply by listing out the possibilities and answering the exact question that is asked. With 3 coins, there are (2)(2)(2) = 8 possible outcomes. They are...
HHH
HHT
HTH
THH
TTT
TTH
THT
HTT
We're asked for the probability of getting exactly 1 HEAD from those 3 tosses. There are three ways (out of 8 total) to get exactly 2 heads (HTT, THT and TTH).
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
Since we're tossing just 3 coins, there aren't that many possible outcomes. This question can be solved simply by listing out the possibilities and answering the exact question that is asked. With 3 coins, there are (2)(2)(2) = 8 possible outcomes. They are...
HHH
HHT
HTH
THH
TTT
TTH
THT
HTT
We're asked for the probability of getting exactly 1 HEAD from those 3 tosses. There are three ways (out of 8 total) to get exactly 2 heads (HTT, THT and TTH).
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
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Jeff@TargetTestPrep
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We need to determine the probability of H-T-T = 1/2 x 1/2 x 1/2 = 1/8.M7MBA 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
Since H-T-T can be arranged in 3!/2! = 3 ways, the total probability is 3/8.
Answer: B
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