If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did : GMAT Data Sufficiency (DS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 17 Jan 2017, 04:34

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Director
Joined: 07 Jun 2004
Posts: 612
Location: PA
Followers: 5

Kudos [?]: 705 [0], given: 22

If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did [#permalink]

### Show Tags

12 Dec 2010, 08:05
2
This post was
BOOKMARKED
00:00

Difficulty:

95% (hard)

Question Stats:

24% (02:32) correct 76% (01:20) wrong based on 79 sessions

### HideShow timer Statistics

If rs ≠ 0, does 1/r + 1/s = 1

(1) rs = 1
(2) s + r = 2.5

Did not understand the OA
[Reveal] Spoiler: OA

_________________

If the Q jogged your mind do Kudos me : )

Math Expert
Joined: 02 Sep 2009
Posts: 36531
Followers: 7070

Kudos [?]: 92963 [2] , given: 10541

Re: DS Algebra [#permalink]

### Show Tags

12 Dec 2010, 08:25
2
KUDOS
Expert's post
1
This post was
BOOKMARKED
rxs0005 wrote:
If rs ≠ 0, does 1/r + 1/s = 1

(1) rs = 1
(2) s + r = 2.5

Did not understand the OA

Is $$\frac{1}{r}+\frac{1}{s}=1$$?

(1) rs = 1 --> $$s=\frac{1}{r}$$ --> question becomes: is $$\frac{1}{r}+r=1$$ --> is $$r^2-r+1=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.
(2) s + r = 2.5 --> $$s=2.5-r$$ --> question becomes: is $$\frac{1}{r}+\frac{1}{2.5-r}=1$$ --> is $$2r^2-5r+5=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.

_________________
Manager
Joined: 19 Apr 2010
Posts: 210
Schools: ISB, HEC, Said
Followers: 4

Kudos [?]: 77 [0], given: 28

Re: DS Algebra [#permalink]

### Show Tags

14 Dec 2010, 03:28
Nice one... Certainly tricky
Manager
Status: Last few days....Have pressed the throttle
Joined: 20 Jun 2010
Posts: 70
WE 1: 6 years - Consulting
Followers: 3

Kudos [?]: 46 [0], given: 27

Re: DS Algebra [#permalink]

### Show Tags

27 Dec 2010, 02:14
Bunuel wrote:
rxs0005 wrote:
If rs ≠ 0, does 1/r + 1/s = 1

(1) rs = 1
(2) s + r = 2.5

Did not understand the OA

Is $$\frac{1}{r}+\frac{1}{s}=1$$?

(1) rs = 1 --> $$s=\frac{1}{r}$$ --> question becomes: is $$\frac{1}{r}+r=1$$ --> is $$r^2-r+1=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.
(2) s + r = 2.5 --> $$s=2.5-r$$ --> question becomes: is $$\frac{1}{r}+\frac{1}{2.5-r}=1$$ --> is $$2r^2-5r+5=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.

A simpler approach would be:
Question is whether -> 1/r + 1/s = 1 or r+s/rs=1....(eq.1)

Stmt 1 -> rs=1 , substituting in (eq.1)

r+s=1 or 1/r+1/s = 1 -> Sufficient

Stmt 1 -> s+r=2.5 , substituting in (eq.1)

2.5/rs=1 => rs=2.5

or 1/r+1/s = 1 -> Sufficient

Ans - D
_________________

Consider giving Kudos if my post helps in some way

Math Expert
Joined: 02 Sep 2009
Posts: 36531
Followers: 7070

Kudos [?]: 92963 [0], given: 10541

Re: DS Algebra [#permalink]

### Show Tags

27 Dec 2010, 02:21
oldstudent wrote:
Bunuel wrote:
rxs0005 wrote:
If rs ≠ 0, does 1/r + 1/s = 1

(1) rs = 1
(2) s + r = 2.5

Did not understand the OA

Is $$\frac{1}{r}+\frac{1}{s}=1$$?

(1) rs = 1 --> $$s=\frac{1}{r}$$ --> question becomes: is $$\frac{1}{r}+r=1$$ --> is $$r^2-r+1=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.
(2) s + r = 2.5 --> $$s=2.5-r$$ --> question becomes: is $$\frac{1}{r}+\frac{1}{2.5-r}=1$$ --> is $$2r^2-5r+5=0$$, no real $$r$$ satisfies this equation (equation has no real roots), so the answer is NO. Sufficient.

A simpler approach would be:
Question is whether -> 1/r + 1/s = 1 or r+s/rs=1....(eq.1)

Stmt 1 -> rs=1 , substituting in (eq.1)

r+s=1 or 1/r+1/s = 1 -> Sufficient

Stmt 1 -> s+r=2.5 , substituting in (eq.1)

2.5/rs=1 => rs=2.5

or 1/r+1/s = 1 -> Sufficient

Ans - D

Answer to the question is indeed D, but I wonder what do the red parts mean in your simpler solution?
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13423
Followers: 575

Kudos [?]: 163 [0], given: 0

Re: If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did [#permalink]

### Show Tags

09 Sep 2016, 04:21
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did   [#permalink] 09 Sep 2016, 04:21
Similar topics Replies Last post
Similar
Topics:
11 If rs#0, is 1/r + 1/s = 4 ? 13 03 Mar 2014, 23:23
2 If rs ≠ 0, is 1/r + 1/s = 3 24 Jan 2011, 03:40
7 If rs#0, is 1/r + 1/s = 4 ? 10 10 Oct 2010, 04:29
Is rs=rx-2? 1. r is odd 2. x=s+2 2 17 May 2010, 12:44
If rs#0, is 1/r + 1/s = 4 ? 13 11 Jun 2007, 21:19
Display posts from previous: Sort by

# If rs 0, does 1/r + 1/s = 1 (1) rs = 1 (2) s + r = 2.5 Did

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.