Is it A?
1/r + 1/s = 4 --> rs * (1/r + 1/s = 4) --> s + r = 4s. This is the same as statement 1. So that is sufficient.
Statement 2: Let's try:
1/s + 1/s = 2/s. Not sufficient, no idea what s is.
Let me know if I'm right.
BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course
Redeem
Featured Course
Target Test Prep GMAT OnDemand
Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.
- 715+ score guarantee — highest in the industry (99th percentile)
- 52 chapters · 1,500+ lessons · 4,000+ practice questions
- 400 hours of video · 1,500+ instructor-led HD smartboard lessons
- 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
- 24/7 live support + weekly Zoom office hours with GMAT instructors
- TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
- 1,200+ flashcards + AI-powered study assistant & daily calendar
- OnDemand, LiveTeach & GMAT Bootcamp formats available
- Also: GRE, SAT Math & Executive Assessment courses
- MBA Admissions Consulting now available
- 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
- 200,000+ students served
- 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★
5.0
(559 reviews)
130-pt guarantee
$0 to start
then $127/mo
Data Sufficiency
Source: Beat The GMAT — Data Sufficiency |
Right, A for me too.
1. s + r = 4rs, same as question, so sufficient
2. r-s = 0, if r & s are +ve fraction then ans to qn stem is true but if they are -ve fractions, then it would be false. so insufficient.
1. s + r = 4rs, same as question, so sufficient
2. r-s = 0, if r & s are +ve fraction then ans to qn stem is true but if they are -ve fractions, then it would be false. so insufficient.
If rs is not equal to 0, is 1/r + 1/s = 4,
can be simplified as (r+s)/rs=4
(1) r + s = 4rs
so
(r+s)/rs=4
=>4rs/rs=4
rs is cancelled, 4=4
insufficient
(2) r = s
so
(r+s)/rs=4
=>2r/rs=4
=>2/4=s
=>s=1/2
and r=1/2
(2) is sufficient, answer is B
can be simplified as (r+s)/rs=4
(1) r + s = 4rs
so
(r+s)/rs=4
=>4rs/rs=4
rs is cancelled, 4=4
insufficient
(2) r = s
so
(r+s)/rs=4
=>2r/rs=4
=>2/4=s
=>s=1/2
and r=1/2
(2) is sufficient, answer is B
oops, sorry, i missed the question details
(1 ) is sufficient to determine, 1/r+1/s=4, as r+s=4rs
so answer should be D
(1 ) is sufficient to determine, 1/r+1/s=4, as r+s=4rs
so answer should be D
Yes, to me it's also D, each is sufficient.[email protected] wrote:oops, sorry, i missed the question details
(1 ) is sufficient to determine, 1/r+1/s=4, as r+s=4rs
so answer should be D
What's the OA please?
Silvia
[email protected] wrote:If rs is not equal to 0, is 1/r + 1/s = 4,
can be simplified as (r+s)/rs=4
(1) r + s = 4rs
so
(r+s)/rs=4
=>4rs/rs=4
rs is cancelled, 4=4
insufficient
(2) r = s
so
(r+s)/rs=4
=>2r/rs=4
=>2/4=s
=>s=1/2
and r=1/2
(2) is sufficient, answer is B
The answer should be A.
The mistake you are making is substituting the statement into what we have to prove.
The approach should be using the statement to prove the question
We are merely given r = s
take r and s as 5
1/5+1/5 is definitely not equal to 4
So statement two is insuff
Keep one thing in mind to avoid these mistakes, that in DS questions the statements will never contradict each other, if one says that x = 2 even the other should imply that. We merely have to decide whether the information will suffice ,it will never contradict
Whether you think you can or can't, you're right.
- Henry Ford
- Henry Ford
1/r + 1/s =r+s/rs - eq1
A)
substituting r + s = 4rs in eq1
4rs/rs=4
hence sufficient
B) substitutin r = s in eq1
2r/r^2=2/r
value of r is not known hence insuffcient
A)
substituting r + s = 4rs in eq1
4rs/rs=4
hence sufficient
B) substitutin r = s in eq1
2r/r^2=2/r
value of r is not known hence insuffcient
vrowland wrote:If rs is not equal to 0, is 1/r + 1/s = 4,
(1) r + s = 4rs
(2) r = s
[/spoiler]
-------------------------------------
--------------------------------------
General blog
https://amarnaik.wordpress.com
MBA blog
https://amarrnaik.blocked/
--------------------------------------
General blog
https://amarnaik.wordpress.com
MBA blog
https://amarrnaik.blocked/
GMAT/MBA Expert
-
Scott@TargetTestPrep
- GMAT Instructor
- Posts: 8139
- Location: Los Angeles, CA
- Thanked: 43 times
Solution:
Question Stem Analysis:
We need to determine whether 1/r + 1/s = 4, i.e., (r + s)/(rs) = 4.
Statement One Alone:
Since r + s = 4rs, we have (r + s)/(rs) = (4rs)/(rs) = 4. Statement one alone is sufficient.
Statement Two Alone:
Statement two is not sufficient. For example, if r = s = 1/2, 1/r + 1/s = 2 + 2 = 4. However, if r = s = 1, 1/r + 1/s = 1 + 1 = 2.
Answer: A
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews
