Last visit was: 24 Apr 2026, 22:23 It is currently 24 Apr 2026, 22:23
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
avatar
rakshitsood21
Joined: 27 Aug 2018
Last visit: 18 Dec 2021
Posts: 27
Own Kudos:
115
 [34]
Given Kudos: 16
Location: India
Concentration: Strategy, Leadership
GMAT 1: 670 Q51 V29
GMAT 2: 740 Q51 V38 (Online)
GPA: 4
GMAT 2: 740 Q51 V38 (Online)
Posts: 27
Kudos: 115
 [34]
Kudos
Add Kudos
34
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
CrackverbalGMAT
User avatar
Major Poster
Joined: 03 Oct 2013
Last visit: 24 Apr 2026
Posts: 4,846
Own Kudos:
9,182
 [9]
Given Kudos: 226
Affiliations: CrackVerbal
Location: India
Expert
Expert reply
Posts: 4,846
Kudos: 9,182
 [9]
5
Kudos
Add Kudos
4
Bookmarks
Bookmark this Post
General Discussion
User avatar
Abhineetegi
Joined: 04 Jan 2018
Last visit: 06 Jul 2021
Posts: 36
Own Kudos:
31
 [3]
Given Kudos: 100
Posts: 36
Kudos: 31
 [3]
2
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
avatar
TheBunk
Joined: 20 Aug 2020
Last visit: 27 May 2022
Posts: 15
Own Kudos:
Given Kudos: 139
Posts: 15
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
CrackVerbalGMAT
\(Time = \frac{Distance}{Speed}\)

Total time when traveling at x miles/hour and y miles/hr = \(\frac{80}{x} + \frac{40}{y}= \frac{80y \space + \space 40x}{xy}\)

When traveling the entire distance at z miles/hr, the time taken = \(\frac{120}{z}\) is 1 hour longer

Therefore \(\frac{120}{z} - (\frac{40x \space + \space 80y}{xy}\)) = 1

In terms of z: \(\frac{120}{z} = (\frac{40x \space + \space 80y}{xy}\)) + 1

\(\frac{120}{z} = \frac{40x \space + \space 80y \space + \space xy}{xy}\)

\(\frac{z}{120} = \frac{xy}{40x \space + \space 80y \space + \space xy}\)

Therefore \(z = \frac{120xy}{40x \space + \space 80y \space + \space xy}\)


Option C

Arun Kumar


Hello,

Thank you for your explanation. However, I don't understand why the Time taken is
\(\frac{80}{x} + \frac{40}{y}= \frac{80y \space + \space 40x}{xy}\)

Souldn't it be
T = 120 / (80/x + 40/y)
since T = D/R ?
User avatar
CrackverbalGMAT
User avatar
Major Poster
Joined: 03 Oct 2013
Last visit: 24 Apr 2026
Posts: 4,846
Own Kudos:
9,182
 [1]
Given Kudos: 226
Affiliations: CrackVerbal
Location: India
Expert
Expert reply
Posts: 4,846
Kudos: 9,182
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
TheBunk



Hello,

Thank you for your explanation. However, I don't understand why the Time taken is
\(\frac{80}{x} + \frac{40}{y}= \frac{80y \space + \space 40x}{xy}\)

Souldn't it be
T = 120 / (80/x + 40/y)
since T = D/R ?


120 = Distance. But in the denominator, when you take 80/x + 40y, this is the sum of the time taken.

In effect you have said that T = Distance/Time which is incorrect.


Total time taken when doing in parts, is the sum of the individual times taken for each of the distances.

So for the 1st 80 miles at x miles/hr, time = 80/x and for the remaining 40 miles at y miles / hr, time = 40 / y. Therefore total time = 80/x + 40/y

When the travel happens without any interruption, then the 120 miles is covered at z miles/hr. Therefor the time here is 120/z


Hope this helps

Arun Kumar
avatar
TheBunk
Joined: 20 Aug 2020
Last visit: 27 May 2022
Posts: 15
Own Kudos:
Given Kudos: 139
Posts: 15
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
CrackVerbalGMAT
TheBunk



Hello,

Thank you for your explanation. However, I don't understand why the Time taken is
\(\frac{80}{x} + \frac{40}{y}= \frac{80y \space + \space 40x}{xy}\)

Souldn't it be
T = 120 / (80/x + 40/y)
since T = D/R ?


120 = Distance. But in the denominator, when you take 80/x + 40y, this is the sum of the time taken.

In effect you have said that T = Distance/Time which is incorrect.


Total time taken when doing in parts, is the sum of the individual times taken for each of the distances.

So for the 1st 80 miles at x miles/hr, time = 80/x and for the remaining 40 miles at y miles / hr, time = 40 / y. Therefore total time = 80/x + 40/y

When the travel happens without any interruption, then the 120 miles is covered at z miles/hr. Therefor the time here is 120/z


Hope this helps

Arun Kumar

It helps a lot! Thanks!
User avatar
Kinshook
User avatar
Major Poster
Joined: 03 Jun 2019
Last visit: 24 Apr 2026
Posts: 5,986
Own Kudos:
Given Kudos: 163
Location: India
GMAT 1: 690 Q50 V34
WE:Engineering (Transportation)
Products:
GMAT 1: 690 Q50 V34
Posts: 5,986
Kudos: 5,859
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Given:To complete a 120-mile trip, a train first travels at a constant rate of x miles per hour (mph) for 80 miles. Then it travels the remaining 40 miles at a constant rate of y mph. If the train had instead completed the entire trip at a constant rate of z mph, the trip would have taken 1 hour longer.

Asked:Which of the following is the value of z in terms of x and y?

120/z - (80/x +49/y) =1
120/z = (80y+40x+xy)/xy
z= 120xy/(80y+40x+xy)

IMO C

Posted from my mobile device
User avatar
UserMaple5
Joined: 27 Apr 2021
Last visit: 24 Jul 2022
Posts: 41
Own Kudos:
Given Kudos: 260
Posts: 41
Kudos: 12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Pick simple numbers to solve.

Let x = 80 mph; so time to to cover 80 miles is 1 hour
Let y = 40 mph; so time to cover 40 miles is 1 hour

Average speed for total trip = 120 miles / 2 hours = 60 mph

At speed z, it would take 1 additional hour to cover 120 miles. So z = 120 miles / (original 2 hours + 1 additional hour)
So z = 120 / 3 = 40 mph

Plug in the values above in the answer choices - you land at C.
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,979
Own Kudos:
Posts: 38,979
Kudos: 1,117
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Math Expert
109818 posts
Tuck School Moderator
853 posts