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Sam flips a coin 12 times.  Find the probability that it comes up heads at least 10 times.

 Jun 8, 2020
 #2
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The probability of it being heads 10 times is (1/2)^10, and since we can have cases for 11 and 12, plus (1/2)^11 and (1/2)^12.

 

So the answer is most definitely not 10/12. An explanation would be helpful?

 Jun 8, 2020
 #3
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12! / [10! . 2!. 2^12] =0.01611328125
12! / [11! . 1!. 2^12] =0.0029296875
12! / [12! . 0!. 2^12] =0.000244140625
The probability of at least 10 heads:
Sum of above 3 =0.019287109375=1.93%, or:
79 / 2^12 =79 / 4096

 Jun 8, 2020
 #4
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+1

Another way:

 

[12C10 + 12C11 + 12C12] =79 / 2^12 =79 / 4096

 Jun 8, 2020
 #5
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Thanks, Guest!

 

laugh

hugomimihu  Jun 8, 2020

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