A jar contains only red and blue marbles in a ratio of 7:3. If there are 18 blue marbles, how many red marbles are there?

Correct answer

B. 42

Explanation

The ratio 7:3 means for every 3 blue marbles there are 7 red. 18 blue ÷ 3 = 6 groups, so red marbles = 7 × 6 = 42.

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