Problem-Solving and Data Analysis practice question

Answer: A. 3/10

Probability = favorable / total = 3 red / (3 + 5 + 2) = 3/10. Choice C forgets to count the red marbles in the total.

Why the other answers are wrong

B. 1/3

1/3 treats the three colors as equally likely, but there are different numbers of each marble — probability is 3 red out of 10 total marbles.

C. 3/7

You put only the non-red marbles (5 + 2 = 7) in the denominator; the total must include the red ones too, giving 3/10.

D. 1/2

5/10 = 1/2 is the probability of drawing blue, not red. The question asks about the 3 red marbles.

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