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a/b

by gmatblood » Sat Nov 05, 2011 8:49 am
If a and b are positive integers such that a/b= 2.86, which of the following must be a divisor of a?

10

13

18

26

50
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by shankar.ashwin » Sat Nov 05, 2011 8:56 am
a/b = 2.86 = 286/100

100a = 286b

(5*5*2*2) a = (2 * 11 * 13) b

therefore, 'a' should be 11 (or) 13. B IMO
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by Anurag@Gurome » Sat Nov 05, 2011 8:58 am
gmatblood wrote:If a and b are positive integers such that a/b= 2.86, which of the following must be a divisor of a?
a/b = 2.86 = 286/100 = 143/50

Hence, 50a = 143b
As 50 and 143 doesn't have any common factor, 143 must be a factor of a.

Now, 143 = 11*13
Hence, 11 and 13 must be factors of a.

The correct answer is B.
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