2012 AMC 12A Problem 4

Problem 4 of 25EasierArithmetic

In a bag of marbles,

\dfrac{3}{5}

of the marbles are blue and the rest are red. If the number of red marbles is doubled and the number of blue marbles stays the same, what fraction of the marbles will be red?

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Solution

Suppose there are

5

marbles:

3

blue and

2

red. Doubling the red gives

4

red while the blue stays at

3.

The total is now

3 + 4 = 7,

so the fraction that is red is

\dfrac{4}{7}.

Thus, the correct answer is C.

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Tagged: fraction · ratio and proportion

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