Last visit was: 10 Jul 2025, 04:02 It is currently 10 Jul 2025, 04:02
Close
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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
Thoughtosphere
Joined: 02 Jul 2012
Last visit: 24 Nov 2021
Posts: 149
Own Kudos:
775
 [26]
Given Kudos: 84
Location: India
Schools: IIMC  (A)
GMAT 1: 720 Q50 V38
GPA: 2.6
WE:Information Technology (Consulting)
Products:
Schools: IIMC  (A)
GMAT 1: 720 Q50 V38
Posts: 149
Kudos: 775
 [26]
2
Kudos
Add Kudos
24
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 10 Jul 2025
Posts: 102,612
Own Kudos:
Given Kudos: 98,069
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 102,612
Kudos: 740,012
 [12]
1
Kudos
Add Kudos
11
Bookmarks
Bookmark this Post
General Discussion
User avatar
Thoughtosphere
Joined: 02 Jul 2012
Last visit: 24 Nov 2021
Posts: 149
Own Kudos:
Given Kudos: 84
Location: India
Schools: IIMC  (A)
GMAT 1: 720 Q50 V38
GPA: 2.6
WE:Information Technology (Consulting)
Products:
Schools: IIMC  (A)
GMAT 1: 720 Q50 V38
Posts: 149
Kudos: 775
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 10 Jul 2025
Posts: 102,612
Own Kudos:
740,012
 [1]
Given Kudos: 98,069
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 102,612
Kudos: 740,012
 [1]
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
Bunuel
Thoughtosphere
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. At what speed, in km/hr, is the car traveling?

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

Time to cover 1 kilometer at 80 kilometers per hour is 1/80 hours = 3,600/80 seconds = 45 seconds;

Time to cover 1 kilometer at regular speed is 45 + 5 = 50 seconds = 50/3,600 hours = 1/72 hours;

So, we get that to cover 1 kilometer 1/72 hours is needed --> regular speed 72 kilometers per hour (rate is a reciprocal of time or rate=distance/time).

Answer: B.

This is a copy of GMAT Prep question discussed here: a-car-traveling-at-a-certain-constant-speed-takes-2-seconds-126658.html
User avatar
manpreetsingh86
Joined: 13 Jun 2013
Last visit: 19 Dec 2022
Posts: 219
Own Kudos:
Given Kudos: 14
Posts: 219
Kudos: 1,147
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Thoughtosphere
Hi Please let me know, whether my approach is correct and whether we can have a faster method to get the right answer

It takes the car 5 sec. longer to travel 1 KM than it would take, had it traveled at 80Kp/Hr
This would mean that it would take the car 200 sec extra had it traveled 40KM
that is equivalent to 10/3 minutes extra to 30 min. it would have taken at 80Km/Hr

Thus it would take 30 + 10/3 minutes to cover 40 Km or 100/3 min = 100/(3*60) hrs

Thus the current speed would be 40*3*60 / 100 = 72 Km/Hr

choice B


time taken to travel 1km at 80km/h = (1/80)*3600 =45 seconds

therefore, first car takes 50 sec to travel 1 km. therefore its speed = (1/50)*3600 =72km/h
User avatar
adiagr
Joined: 18 Jan 2010
Last visit: 05 Oct 2019
Posts: 204
Own Kudos:
Given Kudos: 9
GMAT 1: 710 Q48 V40
Posts: 204
Kudos: 1,097
Kudos
Add Kudos
Bookmarks
Bookmark this Post
UmangMathur
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. At what speed, in km/hr, is the car traveling?

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

Car travelling at 80kmph covers 1 km in (1/80) hrs = \(\frac{60*60}{80}\) = 45 sec.

The other car takes 5 sec more. So the time taken by that car is 50 sec. Distance is 1 Km. So its speed is (1 Km / 50 sec) or

\(\frac{60*60}{50}\) = 72 kmph

B is the answer.
User avatar
gracie
Joined: 07 Dec 2014
Last visit: 11 Oct 2020
Posts: 1,035
Own Kudos:
Given Kudos: 27
Posts: 1,035
Kudos: 1,859
Kudos
Add Kudos
Bookmarks
Bookmark this Post
1k/80kh=1/80h
5 seconds=1/720h
1/80h+1/720h=1/72h
1k/(1/72h)=72kh
User avatar
energetics
Joined: 05 Feb 2018
Last visit: 09 Oct 2020
Posts: 298
Own Kudos:
Given Kudos: 325
Posts: 298
Kudos: 905
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Thoughtosphere
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. At what speed, in km/hr, is the car traveling?

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

(80km / 1hr) * (1hr / 60^2 sec) = 1 km / 45 sec
This is the faster rate, t-5 = 45 sec, so time to travel 1 km at the slower rate is t=50 sec
(Total time of 1 h to travel) 60^2 sec / (time to travel 1 km) 50 sec = 72 km rate of travel in 1h.

Another way, ratio of time taken to travel 1 km is 45/50 = 9/10
9/10 * original rate of 80 km in 1 hr = rate of 72 km / 1 hr

**A good way for me to think about it is that for each 9 iterations of the first rate (at 1 km/45 sec), we need 10 of the 2nd, slower rate (1 km/50 sec) to reach the same distance (since 2nd rate has to catch up by 5 sec every time, after 9 it's a whole extra unit of work).
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 37,373
Own Kudos:
Posts: 37,373
Kudos: 1,010
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderators:
Math Expert
102612 posts
PS Forum Moderator
683 posts