GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 13 Dec 2018, 17:04

### 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

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

## Events & Promotions

###### Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### GMATbuster's Weekly GMAT Quant Quiz, Tomorrow, Saturday at 9 AM PST

December 14, 2018

December 14, 2018

09:00 AM PST

10:00 AM PST

10 Questions will be posted on the forum and we will post a reply in this Topic with a link to each question. There are prizes for the winners.
• ### The winning strategy for 700+ on the GMAT

December 13, 2018

December 13, 2018

08:00 AM PST

09:00 AM PST

What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.

# M17-37

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51185

### Show Tags

16 Sep 2014, 00:02
00:00

Difficulty:

15% (low)

Question Stats:

78% (01:37) correct 22% (01:50) wrong based on 199 sessions

### HideShow timer Statistics

Andrew and Stephen drive on the highway in the same direction at respective rates of 72 and 80 kmh. If Stephen is 4 km behind Andrew, by how much does he have to increase his speed to catch up with Andrew in 20 minutes?

A. 1 kmh
B. 2 kmh
C. 3 kmh
D. 4 kmh
E. 5 kmh

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 51185

### Show Tags

16 Sep 2014, 00:02
1
3
Official Solution:

Andrew and Stephen drive on the highway in the same direction at respective rates of 72 and 80 kmh. If Stephen is 4 km behind Andrew, by how much does he have to increase his speed to catch up with Andrew in 20 minutes?

A. 1 kmh
B. 2 kmh
C. 3 kmh
D. 4 kmh
E. 5 kmh

Denote the required acceleration as $$x$$. The distance between Andrew and Stephen will be decreasing at $$(80 + x - 72)$$ kmh. We can compose the equation $$\frac{4}{80 + x - 72} = \frac{20}{60}$$ from which $$x = 4$$.

_________________
Manager
Joined: 19 Jul 2016
Posts: 50

### Show Tags

29 Jan 2017, 18:24
hi Bunuel

Thnx
Math Expert
Joined: 02 Sep 2009
Posts: 51185

### Show Tags

29 Jan 2017, 23:32
gupta87 wrote:
hi Bunuel

Thnx

Check other solutions here: https://gmatclub.com/forum/andrew-and-s ... 77984.html

Hope it helps.
_________________
Manager
Joined: 09 Oct 2016
Posts: 89
Location: United States
GMAT 1: 740 Q49 V42
GPA: 3.49

### Show Tags

31 May 2017, 05:32
20x=4

x=1/5

x/60 = 1/5

x=12

12-8 = 4

D

Posted from my mobile device
Senior Manager
Joined: 08 Jun 2015
Posts: 436
Location: India
GMAT 1: 640 Q48 V29
GMAT 2: 700 Q48 V38
GPA: 3.33

### Show Tags

31 May 2017, 05:45
The answer has to be option D.

The distance between Andrew and Stephen is 4 Km. We need to find the quantum by which Stephen needs to increase his speed to catch up with Andrew.

4/(x-72)=1/3. Solving for x , we get 84. Andrew needs to increase his speed by 4kmph.
_________________

" The few , the fearless "

Manager
Joined: 27 Mar 2016
Posts: 51

### Show Tags

31 May 2017, 08:55
2
1
In 20 minutes Andrew would cover 72*20/60=24 which means Stephen has to cover 28 km in 20 mins
let the increased speed be x
(80+x)*20/60=28
=>x=4
hence D
DS Forum Moderator
Joined: 21 Aug 2013
Posts: 1412
Location: India

### Show Tags

31 May 2017, 10:10
1
If Stephen has to take a lead of 4 km in 20 minutes, it means he has to take a lead of 12 km in 60 minutes (or 1 hour)
(Just multiplied both with 3, to calculate in km/h)

So their relative speed needs to be 12 km/h. Stephen is right now at 80 km/h and Andrew at 72 km/h. Their relative speed as of now is (80-72) = 8 km/h. So Stephen needs to further increase his speed by (12-8) = 4 km/h

Intern
Joined: 10 May 2017
Posts: 9
Location: India
Concentration: Marketing, Strategy
GMAT 1: 580 Q42 V28
WE: Marketing (Computer Software)

### Show Tags

23 Aug 2018, 19:08
Andrew and Stephen drive on the highway in the same direction at respective rates of 72 and 80 kmh. If Stephen is 4 km behind Andrew, by how much does he have to increase his speed to catch up with Andrew in 20 minutes?

In 20 minutes Andrew can cover (72/3) = 24km. But since he is ahead by 4 km, total distance covered = 24 + 4 = 28km.
In 20 minutes, if Stephen needs to cover 28km, his speed must be 28*3 = 84km/hr. Therefore, he must increase by 4km/hr.
Re: M17-37 &nbs [#permalink] 23 Aug 2018, 19:08
Display posts from previous: Sort by

# M17-37

Moderators: chetan2u, Bunuel

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.