Ratio

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Ratio

by dannya » Wed Jul 11, 2012 12:18 pm
At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders ?

Is there a way to solve this by using a chart ?
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by GMATGuruNY » Wed Jul 11, 2012 1:07 pm
dannya wrote:At a certain school, the ratio of the number of second graders to the number of fourth graders is 8 to 5, and the ratio of the number of first graders to the number of second graders is 3 to 4. If the ratio of the number of third graders to the number of fourth graders is 3 to 2, what is the ratio of the number of first graders to the number of third graders ?

Is there a way to solve this by using a chart ?
FIRST/second = 3/4.
second/fourth = 8/5.
fourth/THIRD = 2/3.

Multiply the ratios so that all of grades in color cancel out:
FIRST/THIRD = FIRST/second * second/fourth * fourth/THIRD = 3/4 * 8/5 * 2/3 = 4/5.
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