Answer:
The answer is 1/16.
Explanation:
The probability of getting a heads first is 1/2. The probability of getting 2 heads in a row is 1/2 of that, or 1/4. The probability of getting 3 heads in a row is 1/2 of that, or 1/8. The probability of getting 4 heads in a row is 1/2 of that, or 1/16.
