|
Author |
Message |
|
TAGS:
|
|
|
VP
Joined: 22 Nov 2007
Posts: 1108
Followers: 6
Kudos [?]:
80
[0], given: 0
|
If x, y, and k are positive numbers such that [#permalink]
 05 Jan 2008, 13:13
If x, y, and k are positive numbers such that 10x/(x+y)+20y/(x+y) = k and if x < y, which of the following could be the value of k?
A. 10
B. 12
C. 15
D. 18
E. 30
|
|
|
|
|
|
|
CEO
Joined: 17 Nov 2007
Posts: 3608
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 240
Kudos [?]:
1322
[0], given: 347
|
Dk=10x/(x+y)+20y/(x+y)=(10x+10y+10y)/(x+y)=10+10*y/(x+y) x<y and x,y are positive: 1/2<y/(x+y)<1 --> 15<k<20 --> k=18
_________________
NEW! GMAT ToolKit 2 (iOS) / GMAT ToolKit (Android) - The must have GMAT prep app | PrepGame
|
|
|
|
|
|
Director
Joined: 12 Jul 2007
Posts: 875
Followers: 8
Kudos [?]:
137
[0], given: 0
|
10x + 20y = k(x+y)
10 = (x+2y) = (x+y) = impossible
12 = (5/6x + 5/3y) = (x+y) = possible
15 = (2/3x + 4/3y) = (x+y) = possible
18 = (5/9x + 10/9y) = (x+y) = possible
30 = (1/3x + 2/3y) = (x+y) = impossible
so now we have three possibilities to narrow down.
for 12: (x-5/6x) = (5/3y-y)
1/6x = 2/3y = impossible since x is smaller than y
for 15: (x-2/3x) = (4/3y-y)
1/3x = 1/3y = impossible since x is smaller than y
for 18: (x-5/9x) = (10/9y -y)
4/9x = 1/9y = possible since x is smaller than y
Answer D
|
|
|
|
|
|
Manager
Joined: 04 Jan 2008
Posts: 86
Followers: 1
Kudos [?]:
10
[0], given: 0
|
D is the answer, by trial and error method. only D satisfies x<y
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Similar topics |
Author |
Replies |
Last post |
|
Similar
Topics:
|
 |
|
|
If x, y, and k are positive numbers such that : (10) +
|
Antmavel |
4 |
16 Oct 2004, 07:03 |
|
|
|
|
If x, y, and k are positive numbers such that
|
lan583 |
8 |
19 Nov 2006, 14:13 |
|
|
|
|
If x, y, and k are positive numbers such that (10) + (20) =
|
suntaurian |
2 |
09 Feb 2008, 16:05 |
 |
5
|
 |
If x, y, and k are positive numbers such that
|
eresh |
31 |
15 Oct 2009, 16:08 |
|
|
3
|
|
If x, y and k are positive numbers such that
|
gmattokyo |
5 |
01 Nov 2009, 21:01 |
|
|
|
|
|
|
close
