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

Redeem
TTP OnDemand GMAT Video Course
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
Start Free 5-Day Trial Read 559 Reviews →

GMAT Prep #2_DS Rates, Distance #33

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members
Location: Milpitas, CA
Thanked: 1854 times
GMAT Score:770

by Anurag@Gurome » Sun Apr 01, 2012 7:48 pm
kwah wrote:Attached is a question from GMAT Prep Test #2.

What is the most efficient way of achieving the result?

Answer: B

Thanks,
K
Let us assume that the average speed of the car = s km/hr, and
time taken to cover 400 km = t hours
Then distance = speed * time implies 400 = st or s = 400/t.

(1) The car traveled the first 200 km in 2.5 hours but we don't know the time taken by the car to travel the second 200 km, NOT sufficient.

(2) If the car's average speed had been 20km per hour greater than it was, it would have traveled the 400km in 1 hour less than it did.
(s + 20)(t - 1) = 400
st + 20t - s - 20 = 400, and st = 400
400 + 20t - s = 420
20t - s = 20
20t - 400/t = 20
20t² - 400 = 20t
20t² - 20t - 400 = 0
t² - t - 20 = 0
(t - 5)(t + 4) = 0
t = 5; SUFFICIENT.

The correct answer is B.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 1248
Joined: Thu Mar 29, 2012 2:57 pmFollowed by: 192 members
Location: Everywhere
Thanked: 503 times
GMAT Score:780

by Bill@VeritasPrep » Sun Apr 01, 2012 7:48 pm
We know that D=RT. From the stem, we know D=400, so our equation is 400=RT. To solve, we'll need some info about the rate.

S1) We have a partial rate, but it's not enough. We could have traveled the remaining 200 km at the same rate, a faster rate, or a slower rate, which means we can come up with different times for the entire trip. Insufficient.

S2) We can set up a new equation. Distance is the same, the rate is 20 km/h faster, and time is 1 hour less:

400=(r+20(t-1)

We now have 2 equations and 2 variables, so we can solve. Sufficient.
Join Veritas Prep's 2010 Instructor of the Year, Matt Douglas for GMATT Mondays

Visit the Veritas Prep Blog

Try the FREE Veritas Prep Practice Test
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1