Question

A fair coin is tossed two times in succession. The set of equally likely outcomes is {HH, HT, TH, TT}. Find the probability of getting exactly one tail.

Answer 1

The event space of getting exactly one tail is {HT, TH}
The sample space is {HH, HT, TH, TT}

There are two ways to get exactly one tail, out of 4 total possible outcomes. 
So 2/4 = 1/2 is the answer