Hi All,
Please help. Don't know how answer is E.
Which of the following CANNOT be the greatest common divisor of two positive integers x and y ?
(A) 1
(B) x
(C) y
(D) x  y
(E) x + Y
Thanks & Regards
Sachin
O.G Quant Review
This topic has expert replies
 sachin_yadav
 Master  Next Rank: 500 Posts
 Posts: 212
 Joined: 06 Dec 2010
 Location: India
 Thanked: 5 times
 Followed by:1 members

 Newbie  Next Rank: 10 Posts
 Posts: 9
 Joined: 25 Dec 2010
 Thanked: 2 times
this can be easily understood as:
1.take any two prime nos. say 2, 3
then G.C.D  1
2. take x=2;y=6
G.C.D. 2=x
3.similarly G.C.D y
4.take x=6;y=4
G.C.D.=2(xy)
so,G.C.D. can't be x+y
or likewise you can understand as G.C.D. is the highest COMMON factors b/w two nos. so their sum can't be so
1.take any two prime nos. say 2, 3
then G.C.D  1
2. take x=2;y=6
G.C.D. 2=x
3.similarly G.C.D y
4.take x=6;y=4
G.C.D.=2(xy)
so,G.C.D. can't be x+y
or likewise you can understand as G.C.D. is the highest COMMON factors b/w two nos. so their sum can't be so
GMAT/MBA Expert
 [email protected]
 GMAT Instructor
 Posts: 3225
 Joined: 08 Jan 2008
 Location: Toronto
 Thanked: 1710 times
 Followed by:613 members
 GMAT Score:800
The only information we have about x and y is that they're positive integers, so there will be very few conclusions we can draw about their greatest common factor.sachin_yadav wrote:Hi All,
Please help. Don't know how answer is E.
Which of the following CANNOT be the greatest common divisor of two positive integers x and y ?
(A) 1
(B) x
(C) y
(D) x  y
(E) x + Y
Thanks & Regards
Sachin
However, here's one thing we do know: the greatest common factor of any positive integer is the integer itself.
Accordingly, there's no way that (x+y), which is greater than each of x and y, could be the greatest common factor of x and y.
Stuart Kovinsky  Kaplan GMAT Faculty  Toronto
Kaplan Exclusive: The Official Test Day Experience  Ready to Take a Free Practice Test?  Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
 sachin_yadav
 Master  Next Rank: 500 Posts
 Posts: 212
 Joined: 06 Dec 2010
 Location: India
 Thanked: 5 times
 Followed by:1 members