Final answer:
The probability of obtaining heads at least once is 7/8.
Step-by-step explanation:
The sample space for flipping a fair coin three times is {HHH, THH, HTH, HHT, TTH, THT, HTT, TTT}.
To find the probability of obtaining heads at least once, we need to count the number of outcomes that have at least one H. There are 7 outcomes that have at least one H (HHH, THH, HTH, HHT, TTH, THT, HTT) out of a total of 8 outcomes in the sample space.
Therefore, the probability of obtaining heads at least once is 7/8.