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mgmat 4

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Senior | Next Rank: 100 Posts
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by simba12123 » Mon Nov 10, 2008 9:03 pm
If x and y are positive integers, which of the following CANNOT be the greatest common divisor of 35x and 20y?


a.5
b.5(x – y)
c.20x
d.20y
e.35x

qa is c

I broke these down to primes and want to deal with the problem in this manner. The mgmat solution is puzzling.
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by cramya » Mon Nov 10, 2008 9:15 pm
https://www.beatthegmat.com/manhattan-gm ... t9454.html

Refer to Stuart's solution.
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Re: mgmat 4

by logitech » Mon Nov 10, 2008 9:26 pm
simba12123 wrote:If x and y are positive integers, which of the following CANNOT be the greatest common divisor of 35x and 20y?


a.5
b.5(x – y)
c.20x
d.20y
e.35x

qa is c

I broke these down to primes and want to deal with the problem in this manner. The mgmat solution is puzzling.
Simba, you probably wonder how D and E CAN be the GCD

35x/20y = 7x/4y Integer ? hmm of Y=7 and X=4 yes

But for C,

20X/35X...X will cancel at both side and you will have 4/7, which is not an integer.
LGTCH
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