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.
mgmat 4
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 94
- Joined: Tue Oct 14, 2008 1:05 pm
- logitech
- Legendary Member
- Posts: 2134
- Joined: Mon Oct 20, 2008 11:26 pm
- Thanked: 237 times
- Followed by:25 members
- GMAT Score:730
Simba, you probably wonder how D and E CAN be the GCDsimba12123 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.
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
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"