The probability of getting a heads on any particular toss is indeed 0.5, but when we are asked what is the probability of getting

heads in a row, we must consider the is asking what is the probability of getting heads the first time AND getting heads the second time AND getting heads the tirhds time all the way yup to

times. So, we apply the special multiplication rule:

This is actually a special case of the binomial probability formula, where the number of favorable outcomes is equal to the number of trials: