Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Sep 1008:00 PM PDT
-09:00 PM PDT
Free- full-length test + 15 concept videos + 150+ short videos + study plan!
Sep 0812:30 AM EDT
-01:30 AM EDT
Looking for your GMAT motivation to break through the score plateau? Pragati improved her score by massive 160 points with strategic guidance and hard-work! Find out how personalized mentorship and a strong mindset can turn GMAT struggles into success.
Sep 1001:00 AM EDT
-02:00 AM EDT
Learn how Keshav, a Chartered Accountant, scored an impressive 705 on GMAT in just 30 days with GMATWhiz's expert guidance. In this video, he shares preparation tips and strategies that worked for him, including the mock, time management, and more.
Sep 1507:00 PM EDT
-09:00 PM EST
Elite scores are possible when you enroll in a powerful GMAT course, taught live online + 6 months access to TTP OnDemand video courses included! Class starts Tues/Thurs Sept. 15, 2026 - Nov. 15, 2027, 7:00pm-9:00pm EST
Sep 2107:00 PM EDT
-10:00 PM EDT
Boost your GMAT score in less than one month in a live online class + 6 months access to TTP OnDemand video courses included! Class starts Mon, Tues, Wed, Thur, Fri Sept. 21, 2026 - Oct. 9, 2027, 7:00pm-10:00pm EST
10 Jul 2025, 08:00
Kudos
Bookmarks
Increased Efficiency: 48 - 0.2R
Decreased Efficiency: 45 - 0.15R
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
60% (02:43) correct
40%
(02:51)
wrong
based on 325
sessions
History
Date
Time
Result
Not Attempted Yet
|
A machine operates at an efficiency of 36 units per liter of fuel when running at exactly 60 rotations per minute (RPM). Its efficiency decreases by 1.2 units for every 8 RPM increase above 60, and increases by 0.8 units for every 4 RPM decrease below 60.
Select for Increased Efficiency a formula for the machine’s efficiency when running at R RPM, where 0 < R < 60 and select for Decreased Efficiency a formula for the machine’s efficiency when running at R RPM, where R > 60. Make only two selections, one in each column.
| Increased Efficiency | Decreased Efficiency | |
| 36 - 0.3R | ||
| 36 + 0.2R | ||
| 45 - 0.15R | ||
| 48 - 0.2R | ||
| 48 + 0.2R | ||
| 60 - 0.25R |
ShowHide Answer
Official Answer
Increased Efficiency: 48 - 0.2R
Decreased Efficiency: 45 - 0.15R
10 Jul 2025, 08:30
Kudos
Bookmarks
Bunuel
GMAT Club Official Explanation:
Increased Efficiency (R < 60):
Efficiency increases by 0.8 units for every 4 RPM below 60.
So, number of 4-RPM drops = (60 - R)/4
Increase = 0.8 * (60 - R)/4
Efficiency = 36 + 0.8 * (60 - R)/4 = 48 - 0.2R
Decreased Efficiency (R > 60):
Efficiency decreases by 1.2 units for every 8 RPM above 60.
So, number of 8-RPM increases = (R - 60)/8
Decrease = 1.2 * (R - 60)/8
Efficiency = 36 - 1.2 * (R - 60)/8 = 45 - 0.15R
General Discussion
10 Jul 2025, 09:08
Kudos
Bookmarks
The formulas for the machine's efficiency are as follows:
For Increased Efficiency (when 0<R<60):
The machine's efficiency increases by 0.8 units for every 4 RPM decrease below 60. This means for every 1 RPM decrease, the efficiency increases by 0.8/4=0.2 units.
The decrease in RPM from 60 is (60−R).
So, the total increase in efficiency is 0.2∗(60−R).
The efficiency formula is 36+0.2∗(60−R)=36+12−0.2R=48−0.2R.
For Decreased Efficiency (when R>60):
The machine's efficiency decreases by 1.2 units for every 8 RPM increase above 60. This means for every 1 RPM increase, the efficiency decreases by 1.2/8=0.15 units.
The increase in RPM from 60 is (R−60).
So, the total decrease in efficiency is 0.15∗(R−60).
The efficiency formula is 36−0.15∗(R−60)=36−0.15R+9=45−0.15R.
Therefore, the correct selections are:
Increased Efficiency: 48−0.2R
Decreased Efficiency: 45−0.15R
For Increased Efficiency (when 0<R<60):
The machine's efficiency increases by 0.8 units for every 4 RPM decrease below 60. This means for every 1 RPM decrease, the efficiency increases by 0.8/4=0.2 units.
The decrease in RPM from 60 is (60−R).
So, the total increase in efficiency is 0.2∗(60−R).
The efficiency formula is 36+0.2∗(60−R)=36+12−0.2R=48−0.2R.
For Decreased Efficiency (when R>60):
The machine's efficiency decreases by 1.2 units for every 8 RPM increase above 60. This means for every 1 RPM increase, the efficiency decreases by 1.2/8=0.15 units.
The increase in RPM from 60 is (R−60).
So, the total decrease in efficiency is 0.15∗(R−60).
The efficiency formula is 36−0.15∗(R−60)=36−0.15R+9=45−0.15R.
Therefore, the correct selections are:
Increased Efficiency: 48−0.2R
Decreased Efficiency: 45−0.15R
