Four fair coins are tossed simultaneously. The probability that at least one…
2002
Four fair coins are tossed simultaneously. The probability that at least one head and one tail turn up is:
- A.
1/16
- B.
1/8
- C.
7/8
- D.
15/16
Attempted by 5 students.
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Correct answer: C
The correct answer is Option C. Four fair coins have 2⁴ = 16 equally likely outcomes. The event “at least one head and one tail” is the complement of getting all heads or all tails. There is 1 all-heads outcome (HHHH) and 1 all-tails outcome (TTTT), so the number of favorable outcomes is 16 - 2 = 14. Hence the probability is 14/16 = 7/8.