7 coins are tossed simultaneously. What is the probability that a tail appears an odd number of times?
As 7 coins are tossed simultaneously the total number of outcomes are 
=128.
The favourable number of outcomes that a tail appears an odd number of times will be, 7C1 + 7C3 + 7C5 + 7C7 = 64.
Thus, the probability
Hence, the probability is 1/2 .
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