A jar contains only red and blue marbles in a ratio of 5:7. If there are 42 blue marbles, how many red marbles are there?

Correct answer

C. 30

Explanation

The ratio 5:7 means for every 7 blue marbles there are 5 red. 42 blue ÷ 7 = 6 groups, so red marbles = 5 × 6 = 30.

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