Question

A recent poll showed that 60% of the residents of the city of renton are democrats. a television reporter would like to interview a local democrat about an upcoming election. if the reporter begins randomly asking people on the street, what is the probability that he will find a democrat by the third person he stops?

Answer 1

The probability is 93.6%.

There are three possibilities for this:  either the first person is a Democrat, the second person is a Democrat, or the third person is a Democrat.  The probabilities for this are:
0.6
0.4(0.6) = 0.24
0.4(0.4)(0.6) = 0.096

Since these are "or"s, we add the together:
0.6+0.24+0.096 = 0.936 = 93.6%