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faisalt
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Marco tosses a coin four times. What is the probability 03 Dec 2005, 12:52
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Marco tosses a coin four times. What is the probability that he get heads exactly twice?

A. 1/4
B. 3/8
C. 7/16
D. 1/2
E. 5/8



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Marco tosses a coin four times. What is the probability 03 Dec 2005, 16:14
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faisalt
Marco tosses a coin four times. What is the probability that he get heads exactly twice?

A. 1/4
B. 3/8
C. 7/16
D. 1/2
E. 5/8
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C(n,k) * p^k * (1-p) ^ n-k

C(4,2)* (1/2)^2*(1/2)^2 = 6*(1/4)*(1/4) = 3/8
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GMATT73
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Marco tosses a coin four times. What is the probability 03 Dec 2005, 22:10
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Probability= #desired results/#possible results (Fastest method)


Total ways to get exactly 2 heads out of 4 flips--->4C2=6

Total possible results--->2^4=16

Put into probability formula--->6/16

Simplify--->3/8
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Marco tosses a coin four times. What is the probability 19 Dec 2005, 23:45
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GMATT73
Probability= #desired results/#possible results (Fastest method)


Total ways to get exactly 2 heads out of 4 flips--->4C2=6

Total possible results--->2^4=16

Put into probability formula--->6/16

Simplify--->3/8
Show more


I came across this problem. I am not sure of the logic behind the bolded part above. I understand total possible results are 2^4, but can someone please explain how the total ways to get exactly 2 heads out of 4 flips is 4C2? Thanks
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Marco tosses a coin four times. What is the probability 20 Dec 2005, 00:48
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yb
GMATT73
Probability= #desired results/#possible results (Fastest method)


Total ways to get exactly 2 heads out of 4 flips--->4C2=6

Total possible results--->2^4=16

Put into probability formula--->6/16

Simplify--->3/8

I came across this problem. I am not sure of the logic behind the bolded part above. I understand total possible results are 2^4, but can someone please explain how the total ways to get exactly 2 heads out of 4 flips is 4C2? Thanks
Show more


What we're concerned here is how to pick a group of n objects from a pool of p objects. The way to calculate this is to use combinations and 4C2 represents 2 heads out of 4 tosses.

Another way to do this:
Possible arrangements:
TTHH
THTH
HTHT
HHTT
HTTH
THHT

Total number of arrangements = 16
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Marco tosses a coin four times. What is the probability 20 Dec 2005, 03:41
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faisalt
Marco tosses a coin four times. What is the probability that he get heads exactly twice?

A. 1/4
B. 3/8
C. 7/16
D. 1/2
E. 5/8
Show more


Total number of combinations = 16
Number of ways to choose heads twice = 4c2 = 6
= 6/16 = 3/8
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Marco tosses a coin four times. What is the probability 20 Dec 2005, 11:38
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ywilfred
yb
GMATT73
Probability= #desired results/#possible results (Fastest method)


Total ways to get exactly 2 heads out of 4 flips--->4C2=6

Total possible results--->2^4=16

Put into probability formula--->6/16

Simplify--->3/8

I came across this problem. I am not sure of the logic behind the bolded part above. I understand total possible results are 2^4, but can someone please explain how the total ways to get exactly 2 heads out of 4 flips is 4C2? Thanks

What we're concerned here is how to pick a group of n objects from a pool of p objects. The way to calculate this is to use combinations and 4C2 represents 2 heads out of 4 tosses.

Another way to do this:
Possible arrangements:
TTHH
THTH
HTHT
HHTT
HTTH
THHT

Total number of arrangements = 16
Show more


Thanks ywilfred. This is how I understand it... 4 ways to pick the first head, 3 to pick the second, divide by 2 to prevent double counting.



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Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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