A coin is tossed 5 times. What is the probability that a head appears an even number of times?
As the coin is tossed 5 times the total number of outcomes will be 
.
And we know that the favourable outcomes of a head appearing even number of times will be,
That either the head appears 0, 2 or 4 times so,
The respective probabilities will be:- 5C0 + 5C2 + 5C4 = 16
Thus, the probability
⇒ 
Hence, the probability is 1/2.
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