math
posted by raja harishchandra .
A fair coin is flipped 3 times. The probability of getting exactly two heads, given that at least one flip results in a head, can be written as a/b, where a and b are coprime positive integers. What is the value of a+b?

please answer

its urgent

10

10 looks good to me.
Of the 8 possible outcomes, 7 have at least one head
3 of those have exactly 2 heads. 
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chal le tere liye answer...gift..........................2