Last visit was: 29 Apr 2026, 13:38

It is currently 29 Apr 2026, 13:38

Toolkit

Practice Tests

Quantitative Questions

Problem Solving (PS)

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.

Go to My Error Log Learn more

Request Expert Reply

Confirm Cancel

Back to Forum

Create Topic

A driver completed the first 20 miles of a 40-mile trip at an average

1 2

KarishmaB

Tutor

Joined: 16 Oct 2010

Last visit: 28 Apr 2026

Posts: 16,447

Own Kudos:

79,447

[2]

Given Kudos: 485

Location: Pune, India

Products:

Expert

Expert reply

Posts: 16,447

Kudos: 79,447

[2]

12 Apr 2018, 21:18

Kudos

Bookmarks

asfandabid

VeritasPrepKarishma

I figured out. Sorry!

It's like:

t1/t2=(x-60)/(60-50)

Where t1= 2/5 & t2= 20/x

The equation looks something like this after solving a bit
2x/5*20=(x-60)/10
x=5(x-60)
X=5x-300
4x=300
x= 75

Option D

Though you have applied the scale method correctly, I would like to point out that the best method to use here is the formula 2ab/(a+b)
When one drives at speed a for half the distance and at speed b for the other half of the distance, the average speed is given by 2ab/(a+b)

60 = 2*50*b/(50 + b)
b = 3000/40 = 75

Check this post for these formulas: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2015/0 ... -the-gmat/

Bambi2021

Joined: 13 Mar 2021

Last visit: 23 Dec 2021

Posts: 306

Own Kudos:

142

[1]

Given Kudos: 226

Posts: 306

Kudos: 142

[1]

29 Jun 2021, 23:26

Kudos

Bookmarks

Average speed when a body covers m part of the trip at speed x and the second n part of the trip at speed y:

average speed = (m+n)xy / (my+nx)

60 = (20+20)50x / (20*50 + 20x)

60 = 2000x / 1000 + 20x

60 000 = 800x

x = 75

Questions of speed, distance, work and time are the few types of questions where I really prefer to use memorized formulas.

Kavicogsci

Joined: 13 Jul 2024

Last visit: 09 Feb 2025

Posts: 157

Own Kudos:

102

Given Kudos: 154

GMAT 1: 710 Q48 V40 Verified score

Posts: 157

Kudos: 102

18 Aug 2024, 20:19

Kudos

Bookmarks

I solved this in 40 seconds so sharing a quick solution
When distances are same and you have travelled with u rate for x distance and y rate for another x distance avg speed is 2uv/(u+v)

We can see that the distances are same here - so that shouldnt be an issue for formula
Let v be the speed of the second leg of the journey
2(50)(v)/(50+v)= 60
Solve to get v 75

e3thekid

Joined: 31 Mar 2022

Last visit: 26 Apr 2026

Posts: 72

Own Kudos:

Given Kudos: 144

Location: United States

Posts: 72

Kudos: 34

18 Aug 2024, 21:11

Kudos

Bookmarks

Bunuel

A driver completed the first 20 miles of a 40-mile trip at an average speed of 50 miles per hour. At what average speed must the driver complete the remaining 20 miles to achieve an average speed of 60 miles per hour for the entire 40-mile trip? (Assume that the driver did not make any stops during the 40-mile trip.)

(A) 65 mph
(B) 68 mph
(C) 70 mph
(D) 75 mph
(E) 80 mph

We can use the average speed formula:
Average speed = Total Distance / Total Time (time for first 20 miles + time for last 20 miles)

60 = 40/ 20/50 + 20/x

60 = 40/ 20x/50x + 1000/50x

60 = 40 / 20x + 1000/50x

60 = 2000x / 20x + 1000

1200x + 60000 = 2000x
60000 = 800x
600/8 = x
75 = x

IMO Option D

Posted from my mobile device

Aboyhasnoname

Joined: 19 Jan 2025

Last visit: 29 Apr 2026

Posts: 302

Own Kudos:

100

Given Kudos: 64

Products:

Posts: 302

Kudos: 100

24 Jun 2025, 03:53

Kudos

Bookmarks

Hi Is this the right approach?

From 50 I need to make my avg speed 60..that means It should be minimum of 70......but since.....the first half will take more time...So the second half should be somewhat higher than this ....among the options..75 seems the right option...Is this approach risky?

KarishmaB

It's an instinctive method you often use when you learn to play with numbers in your head.
You want the average speed to be 60 miles/hr i.e. you need to cover 60 miles in 60 mins which means you must cover 40 miles in 40 mins.
The first 20 miles were covered at an average speed of 50 mph i.e. time taken (in mins) to cover the first 20 miles is 20/50 * 60 = 24 mins
You need to cover 40 miles in total 40 mins and you have already taken 24 mins during the first 20 miles. This means, you need to speed up now and cover the rest of the 20 miles in the leftover 16 mins.
What will be your speed in mph if you cover 20 miles in 16/60 hrs?
Speed = 20/(16/60) = 75 mph