• FREE GMAT Exam
Know how you'd score today for $0 Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • 5 Day FREE Trial Study Smarter, Not Harder Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• Get 300+ Practice Questions

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

## A car traveling at a certain constant speed...

tagged by: BTGmoderatorLU

This topic has 3 expert replies and 0 member replies

### Top Member

BTGmoderatorLU Moderator
Joined
15 Oct 2017
Posted:
559 messages
Followed by:
5 members

#### A car traveling at a certain constant speed...

Tue Feb 27, 2018 10:53 am
A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling?

A. 70
B. 72
C. 74
D. 75
E. 78

The OA is B.

I know that 1 kilometer at 80 km/h is covered in a time = 1/80 hours, in seconds will be 3600/80 = 45 seconds. I stuck here.

I'm confused by this PS question. Experts, any suggestion about how can I solve it? Thanks in advance.

### GMAT/MBA Expert

Rich.C@EMPOWERgmat.com Elite Legendary Member
Joined
23 Jun 2013
Posted:
9602 messages
Followed by:
482 members
2867
GMAT Score:
800
Tue Feb 27, 2018 4:47 pm
Hi LUANDATO,

We're told that a car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/hour. We're asked at what speed, in km/hour, the car is traveling.

Your 'first step' - to convert km/hour into seconds/km is perfect. Since there are 3600 seconds per hour, it would take 3600/80 = 45 seconds to travel 1 km when traveling 80km/hour.

We're told that it takes 5 seconds LONGER to travel that same distance, so we now have to add those 5 seconds and 'work backwards' to find the speed...

(45+5) = 50 seconds to travel 1 km

Since there are 3600 seconds per hour, then we would end up traveling 3600/50 = 72 km in one hour. Thus, the speed is 72 km/hour.

GMAT assassins aren't born, they're made,
Rich

_________________
Contact Rich at Rich.C@empowergmat.com

### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
Joined
25 May 2010
Posted:
14443 messages
Followed by:
1834 members
13060
GMAT Score:
790
Wed Feb 28, 2018 3:45 am
LUANDATO wrote:
A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling?

A. 70
B. 72
C. 74
D. 75
E. 78
80 kilometers per hour = 80 kilometers in 3600 seconds.
A car takes 5 seconds longer.
Since 1 kilometer takes 5 seconds longer, 80 kilometers takes 400 seconds longer, implying a rate of 80 kilometers in 4000 seconds:
(80 kilometers)/(4000 seconds) * (3600 seconds)/(1 hour) = 72 kph.

_________________
Mitch Hunt
GMAT Private Tutor
GMATGuruNY@gmail.com

If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.

Available for tutoring in NYC and long-distance.
Student Review #1
Student Review #2
Student Review #3

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

### GMAT/MBA Expert

Scott@TargetTestPrep GMAT Instructor
Joined
25 Apr 2015
Posted:
1209 messages
Followed by:
8 members
43
Thu Mar 01, 2018 5:39 pm
LUANDATO wrote:
A car traveling at a certain constant speed takes 5 seconds longer to travel 1 km than it would take to travel 1 km at 80 km/h. At what speed, in km/h, is the car traveling?

A. 70
B. 72
C. 74
D. 75
E. 78
If a car is traveling at 80 km per hour, then the number of seconds (x) it takes to travel 1 km can be calculated using the following proportion (note that 1 hour = 3,600 seconds):

80/3600 = 1/x

80x = 3600

x = 45 sec

Thus, it takes 45 seconds to travel 1 km if the speed is 80 km/h. Since the car actually takes 5 more seconds (i.e., 50 seconds) to travel 1 km, its speed (r) can be calculated using the following proportion:

r/3600 = 1/50

50r = 3600

r = 72 km/h

_________________
Scott Woodbury-Stewart Founder and CEO

### Top First Responders*

1 GMATGuruNY 103 first replies
2 Brent@GMATPrepNow 43 first replies
3 Rich.C@EMPOWERgma... 34 first replies
4 Jay@ManhattanReview 29 first replies
5 Scott@TargetTestPrep 11 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

### Most Active Experts

1 GMATGuruNY

The Princeton Review Teacher

152 posts
2 Brent@GMATPrepNow

GMAT Prep Now Teacher

139 posts
3 Scott@TargetTestPrep

Target Test Prep

104 posts
4 Max@Math Revolution

Math Revolution

86 posts
5 Rich.C@EMPOWERgma...

EMPOWERgmat

86 posts
See More Top Beat The GMAT Experts