A fair coin is flipped 7 times. What is the probability that at least 5 of the flips come up heads? Give your answer as a simplified fraction.
At least 5 heads out of 7 flips:
The probability is:
(7 nCr 5)+(7 nCr 6)+(7 nCr 7) / 2^7 =29 / 128
+49 
