SAT Probability and conditional probability Practice Question 8 (Hard)

Question bank / Probability and conditional probability

Math · Problem-Solving and Data AnalysisHard

Age group	Online	Television	Total
18–34	96	24	120
35–54	84	66	150
55+	39	91	130
Total	219	181	400

The table summarizes the results of a survey of $400$ adults about their primary source of news. If one adult is selected at random from those who are NOT in the 18–34 age group, what is the probability that the adult's primary news source is television?

$\frac{157}{280}$

$\frac{157}{181}$

$\frac{157}{400}$

$\frac{181}{400}$

Show answer and explanation

Answer: A

Adults not in the 18–34 group are in the 35–54 or 55+ groups: $150 + 130 = 280$ adults. Of these, $66 + 91 = 157$ chose television. The probability is $\frac{157}{280}$ .

Choice B divides by all television viewers ( $181$ ), which answers a different question: the probability that a TV viewer is not aged 18–34.

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