If you were to flip a coin 4 times what is the probability of getting heads at least one time?

As the question is "what is the probability of getting at least one head" the correct way to answer this is to ask what is the probability of not getting any heads and then subtract this from 1.

The probability of not getting a head in 4 flips = 0.54 (i.e. 0.5 * 0.5 * 0.5 * 0.5) = 1/16.

Therefore the probability of getting at least one head is 1 - 1/16 = 15/16.