The probability of tossing at least two tails when a fair coin is tossed three times can be calculated as follows:
There are 2 possible outcomes for each coin toss (head or tail). Since the coin is fair, each outcome has an equal probability of 1/2.
To calculate the probability of tossing at least two tails, we need to consider the following possibilities:
1. TTT (3 tails)
2. TTH (2 tails, 1 head)
3. THT (2 tails, 1 head)
4. HTT (2 tails, 1 head)
5. THH (1 tail, 2 heads)
6. HTH (1 tail, 2 heads)
7. HHT (1 tail, 2 heads)
8. HHH (3 heads)
Out of these 8 possible outcomes, 3 of them have at least two tails (TTT, TTH, HTT).
Therefore, the probability of tossing at least two tails is 3/8, which corresponds to the answer choice "three eighths".