A jar contains only red and blue marbles in a ratio of 3:7. If there are 28 blue marbles, how many red marbles are there?

Correct answer

D. 12

Explanation

The ratio 3:7 means for every 7 blue marbles there are 3 red. 28 blue ÷ 7 = 4 groups, so red marbles = 3 × 4 = 12.

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