Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

the R-scale and the S-scale

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 234
Joined: Tue May 31, 2016 1:40 am
Thanked: 3 times
by Needgmat » Sat Aug 27, 2016 9:36 am
A certain quantity is measured on two different scale, the R-scale and the S-scale, that are related linearly. Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively. What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A) 20

B) 36

C) 48

D) 60

E) 84

OAC

Please explain. I don't understand what to do.

Many thanks in advance.

Kavin
Top
Join the discussion
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Sat Aug 27, 2016 9:42 am
A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly. Measurements on the R-scale of 6 and 24 correspond to measurements on the S-scale of 30 and 60, respectively. What measurement on the R-scale corresponds to a measurement of 100 on the S-scale?

A. 20
B. 36
C. 48
D. 60
E. 84
Since the relationship between R and S is linear, any pair of points (R,S) must yield the same slope.

Given points are (6,30), and (24,60).
Slope = (S₂ - S�)/(R₂ - R�) = (60-30)/(24-6) = 30/18 = 5/3.

(6,30) and (R,100) must yield the same slope.
(100-30)/(R-6) = 5/3.
70/(R-6) = 5/3.
Cross-mulitplying, we get:
5R-30 = 210.
R = 48.

The correct answer is C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 234
Joined: Tue May 31, 2016 1:40 am
Thanked: 3 times

by Needgmat » Sat Aug 27, 2016 8:33 pm
Since the relationship between R and S is linear, any pair of points (R,S) must yield the same slope.

Given points are (6,30), and (24,60).
Slope = (S₂ - S�)/(R₂ - R�) = (60-30)/(24-6) = 30/18 = 5/3.

(6,30) and (R,100) must yield the same slope.
(100-30)/(R-6) = 5/3.
70/(R-6) = 5/3.
Cross-mulitplying, we get:
5R-30 = 210.
R = 48.

The correct answer is C.
Hi GMATGuruNY ,

Thank you so much for your reply.

But how do we come to know that we have to find slope in this question?

Fist time I saw this question. I got blank totally.

Please explain.

Many thanks in advance.

Kavin
Top
Join the discussion
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Mon Aug 29, 2016 11:06 pm
Needgmat wrote:
Hi GMATGuruNY ,

Thank you so much for your reply.

But how do we come to know that we have to find slope in this question?

Fist time I saw this question. I got blank totally.

Please explain.

Many thanks in advance.

Kavin
The problem above is the same as the following:

A certain quantity is measured on two different axes, the x-axis and the y-axis, that are related linearly. Measurements on the x-axis of 6 and 24 correspond to measurements on the y-axis of 30 and 60, respectively. What measurement on the x-axis corresponds to a measurement of 100 on the y-axis?

To be related linearly = to lie on the same line.
Thus, all three points -- (6,30), (24,60) and (x,100) -- lie on the same line.
Slope = (y₂ - y�)/(x₂ - x�).
The equation above must hold for any ANY TWO POINTS on the line.
Thus, (6,30) and (x,100) must yield the same slope as (6,30) and (24,60).
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
GMAT Instructor
Posts: 2629
Joined: Wed Sep 12, 2012 3:32 pmFollowed by: 119 members
Location: East Bay all the way
Thanked: 625 times
GMAT Score:780

by Matt@VeritasPrep » Thu Sep 01, 2016 5:41 pm
Needgmat wrote: But how do we come to know that we have to find slope in this question?
If we say that r and s are related linearly, we're really saying that r and s have the relationship s = r*m + b ... which is just our boring old y = mx + b equation with r and s replacing x and y.

Since we have s = r*m + b, we then plug in the points we're given, and solve for m and b:

if r = 6, then s = 30, so 30 = 6m + b
if r = 24, then s = 60, so 60 = 24m + b

From there, you have two variables, two equations, so you can solve for m and b, then use the equation of the line.
Top
Join the discussion
GMAT Instructor
Posts: 2629
Joined: Wed Sep 12, 2012 3:32 pmFollowed by: 119 members
Location: East Bay all the way
Thanked: 625 times
GMAT Score:780

by Matt@VeritasPrep » Thu Sep 01, 2016 5:43 pm
There's also a nice way of cheating this problem. Since we're told that for one set of points, S doubles when R quadruples, we can roughly guess that R will approximately double if S goes up by 50%.

Since S is going from 60 to 100, it's going up by a little more than 50%. That means R should more or less double, so our answer should be about 24*2, or 48. Lo and behold, it's exactly 48, and we're good to go.

This isn't the most reliable method in the world, but it's sound enough here if you only have 10 seconds left to try the problem.
Top
Join the discussion