Question 9 The sample space for tossing three fair coins is [HHH, HHT, HTH, HTT, THH, THT, TTH, TIT] What is the probability of tossing exactly one head? $3 / 8$ $1 / 2$ $1 / 8$ $50 / 50$

Step 1 ：The question is asking for the probability of tossing exactly one head when tossing three fair coins. The sample space provided shows all possible outcomes of this event.

Step 2 ：To find the probability, we need to count the number of outcomes that have exactly one head and divide by the total number of outcomes.

Step 3 ：The sample space for this event is \(['HHH', 'HHT', 'HTH', 'HTT', 'THH', 'THT', 'TTH', 'TTT']\).

Step 4 ：The outcomes that have exactly one head are \(['HTT', 'THT', 'TTH']\).

Step 5 ：So, the probability is \(\frac{3}{8}\).

Step 6 ：Final Answer: The probability of tossing exactly one head when tossing three fair coins is \(\boxed{\frac{3}{8}}\).