To find the chance of A or B happening, add their probabilities and then subtract the probability that:
AB is certain
BBoth happen
CNeither happens
DA happens twice
Answer & Solution
Correct answer: B. Both happen
1. Adding counts the overlap in both terms.
2. That overlap has been included twice.
3. So subtract P(A and B) once to correct it.
_Source: OpenStax Introductory Statistics 2e, Chapter 3, Probability Topics._
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