SAT Probability and conditional probability Practice Question 1 (Easy)

Question bank / Probability and conditional probability

Math · Problem-Solving and Data AnalysisEasy

A bag contains $6$ red marbles, $9$ blue marbles, and $5$ green marbles. If one marble is selected at random, what is the probability that it is green?

$\frac{1}{4}$

$\frac{1}{3}$

$\frac{1}{5}$

$\frac{3}{4}$

Show answer and explanation

Answer: A

There are $6 + 9 + 5 = 20$ marbles in total, and $5$ of them are green. The probability is $\frac{5}{20} = \frac{1}{4}$ .

Choice B uses $\frac{5}{15}$ , comparing green marbles to non-green marbles instead of to all marbles.

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