BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Manhattan CAT

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Tue Mar 17, 2009 3:59 pm

Manhattan CAT

by gbb » Fri Mar 27, 2009 8:40 pm
What is the ratio of r to s?
(i) r + s = 7
(ii) r^2 – s^2 = 7

answer C.





not clear why not B?

(ii) r^2 – s^2 = 7

(r + s)(r – s) = 7

the only possible values to satisfy this equation are r=4, s=3, right?
Top
Source: — Data Sufficiency |
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pm
Thanked: 331 times
Followed by:11 members

by cramya » Fri Mar 27, 2009 8:54 pm
r and s can be -4 and 3 which makes it a negative ratio.

Its not given r and s are positive integers.
Top
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pm
Location: Toronto
Thanked: 1710 times
Followed by:614 members
GMAT Score:800

Re: Manhattan CAT

by Stuart@KaplanGMAT » Fri Mar 27, 2009 9:24 pm
gbb wrote:What is the ratio of r to s?
(i) r + s = 7
(ii) r^2 – s^2 = 7

answer C.





not clear why not B?

(ii) r^2 – s^2 = 7

(r + s)(r – s) = 7

the only possible values to satisfy this equation are r=4, s=3, right?
Nowhere does it say that r and s are integers.

Going back to the original statement, we could have:

r^2 = 8 and s^2 = 1
r^2 = 9 and s^2 = 2
r^2 = 10 and s^2 = 3

and on and on and on...
Image

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
Top
Post new topic Post Reply
• Page 1 of 1