alleryStart learning →A penny and a quarter are flipped together. What is the chance of getting exactly one head and one tail?
A1/4
B1/8
C3/4
D1/2
Answer & Solution
Correct answer: D. 1/2
1. Two separate cases give one head and one tail: penny heads with quarter tails, or quarter heads with penny tails.
2. Each case needs two independent results, so use the product rule: 1/2 times 1/2 equals 1/4.
3. The two cases are mutually exclusive, so the word or signals the sum rule.
4. Add them: 1/4 plus 1/4 equals 1/2.
5. Listing all four outcomes gives HH, HT, TH and TT, and two of those four are mixed, again 1/2.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 12 "Mendel's Experiments and Heredity", section 12.1 Mendel's Experiments and the Laws of Probability_
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