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

 It is currently 14 Dec 2018, 17:09

### 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
• ### Typical Day of a UCLA MBA Student - Recording of Webinar with UCLA Adcom and Student

December 14, 2018

December 14, 2018

10:00 PM PST

11:00 PM PST

Carolyn and Brett - nicely explained what is the typical day of a UCLA student. I am posting below recording of the webinar for those who could't attend this session.
• ### Free GMAT Strategy Webinar

December 15, 2018

December 15, 2018

07:00 AM PST

09:00 AM PST

Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

# The time it took car A to travel 400 miles was 2 hours less than the

Author Message
TAGS:

### Hide Tags

Intern
Joined: 26 Feb 2011
Posts: 32
The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

10 Mar 2011, 09:42
1
13
00:00

Difficulty:

45% (medium)

Question Stats:

73% (02:37) correct 27% (03:11) wrong based on 251 sessions

### HideShow timer Statistics

The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed in miles per hour?

A. 20
B. 30
C. 40
D. 50
E. 80
Retired Moderator
Joined: 20 Dec 2010
Posts: 1820
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

10 Mar 2011, 10:02
Let B's average speed be b

$$\frac{400}{b+10} = \frac{400}{b}-2$$

$$\frac{400}{b+10} = \frac{400}{b}-2$$

$$(b+50)(b-40)=0$$

b=40 miles/h

Ans: "C"
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 51215
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

10 Mar 2011, 10:08
1
2
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed in miles per hour?

A. 20
B. 30
C. 40
D. 50
E. 80

Let the rate of B be $$x$$ miles per hour, then the rate of A would be $$x+10$$ miles per hour.

We also know that the time of B equals to time of A + 2: $$\frac{400}{x}=\frac{400}{x+10}+2$$, from this point it's better to plug the answer choices rather than to solve the quadratics. You can quickly find that $$\frac{400}{40}=10=\frac{400}{40+10}+2=8+2$$

_________________
SVP
Joined: 06 Sep 2013
Posts: 1721
Concentration: Finance
The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

31 Dec 2013, 10:44
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed in miles per hour?

A. 20
B. 30
C. 40
D. 50
E. 80

Agree with Bunuel, in these problems one will find it easier to plug in answer choices, that is, backsolving

One gets

400/B+10 - 400/B = 2

So beginning with C one gets that 10 - 8 = 2

So bingo!

Cheers!
J
Intern
Joined: 05 Dec 2013
Posts: 14
The time it took car A to travel 400 miles was 2 hours less  [#permalink]

### Show Tags

31 Dec 2013, 13:49
Bunuel wrote:
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed in miles per hour?

A. 20
B. 30
C. 40
D. 50
E. 80

Let the rate of B be $$x$$ miles per hour, then the rate of A would be $$x+10$$ miles per hour.

We also know that the time of B equals to time of A + 2: $$\frac{400}{x}=\frac{400}{x+10}+2$$, from this point it's better to plug the answer choices rather than to solve the quadratics. You can quickly find that $$\frac{400}{40}=10=\frac{400}{40+10}+2=8+2$$

I'm struggling with this one for some odd reason:

The setup for my work was as follows
Car B: Rate = R + 10, Time = T + 2, Distance = 400
Car A: Rate = R, Time = T, Distance = 400

I then substituted B's Rate (400/T) into Ys equation --> giving me --> (400 / T) + 10 = (400 / T - 2)
After solving this out, I got T = 20, therefore Car B's average speed is 20mph.

Can either of you help me out with where I went wrong here. Much appreciated. Just over a month from my first GMAT experience!
Math Expert
Joined: 02 Sep 2009
Posts: 51215
The time it took car A to travel 400 miles was 2 hours less  [#permalink]

### Show Tags

01 Jan 2014, 04:57
bparrish89 wrote:
Bunuel wrote:
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A's average speed was 10 miles per hour greater than that of car B, what was car B's average speed in miles per hour?

A. 20
B. 30
C. 40
D. 50
E. 80

Let the rate of B be $$x$$ miles per hour, then the rate of A would be $$x+10$$ miles per hour.

We also know that the time of B equals to time of A + 2: $$\frac{400}{x}=\frac{400}{x+10}+2$$, from this point it's better to plug the answer choices rather than to solve the quadratics. You can quickly find that $$\frac{400}{40}=10=\frac{400}{40+10}+2=8+2$$

I'm struggling with this one for some odd reason:

The setup for my work was as follows
Car B: Rate = R + 10, Time = T + 2, Distance = 400
Car A: Rate = R, Time = T, Distance = 400

I then substituted B's Rate (400/T) into Ys equation --> giving me --> (400 / T) + 10 = (400 / T - 2)
After solving this out, I got T = 20, therefore Car B's average speed is 20mph.

Can either of you help me out with where I went wrong here. Much appreciated. Just over a month from my first GMAT experience!

We are given that Car As average speed was 10 miles per hour greater than that of car B, thus if you say that the rate of A is R miles per hour, then the rate of B is R-10 miles per hour (not R+10).

The equation should be 400/T -10 = 400/(T+2) --> T=8 --> B's rate = 400/(T+2) = 40.

Hope it's clear.
_________________
Director
Joined: 23 Jan 2013
Posts: 568
Schools: Cambridge'16
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

22 Jun 2014, 21:13
To be academic with use GMAT strategy)

R * T = D
A x-2= 400
B x = 400

Question is what is the rate of B. I agree that backsolving is the best strategy and start with C. If R of B=40 then x=10 and R of A=50 and this is 10 more than B. So answer is C
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1825
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

22 Jun 2014, 21:46
1
.......................... A................. B

Time .................. t .................. t+2

Speed ............... s+10 ............... s

t(s+10) = s(t+2) = 400

s = 5t

Substitute value of t in any of the formed equation:

$$\frac{s}{5} (s+10) = 400$$

$$s^2 + 10s - 2000 = 0$$

Speed of B (s) = 40

_________________

Kindly press "+1 Kudos" to appreciate

Intern
Joined: 14 Jun 2014
Posts: 2
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

03 Jul 2014, 09:45
The first step should be mentioned here: Translate the task into numbers and variables !

Here you have a lot of different possibilities just 2 examples:

I. (r+10) * (t-2) =400
II. r * t = 400

OR:

I. (r+10) * t = 400
II. r * (t+2) = 400

As you can see, no we have 2 equations with 2 variables... tons of different possibilities to solve this as well:
Manager
Joined: 10 Apr 2018
Posts: 180
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

11 Aug 2018, 13:00
Bunuel wrote:
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car As average speed was 10 miles per hour greater than that of car B, what was car Bs average speed in miles per hour?
A/ 20
B/ 30
C/ 40
D/ 50
E/ 80

Let the rate of B be $$x$$ miles per hour, then the rate of A would be $$x+10$$ miles per hour.

We also know that the time of B equals to time of A + 2: $$\frac{400}{x}=\frac{400}{x+10}+2$$, from this point it's better to plug the answer choices rather than to solve the quadratics. You can quickly find that $$\frac{400}{40}=10=\frac{400}{40+10}+2=8+2$$

Hi Bunuel,
This question needs an edit.
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A ‘s average speed was 10 mi greater than that of average speed of Car B , the what was Car B’s average speed in miles per hour?

Probus
Math Expert
Joined: 02 Sep 2009
Posts: 51215
Re: The time it took car A to travel 400 miles was 2 hours less than the  [#permalink]

### Show Tags

11 Aug 2018, 13:23
Probus wrote:
Bunuel wrote:
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car As average speed was 10 miles per hour greater than that of car B, what was car B`s average speed in miles per hour?
A/ 20
B/ 30
C/ 40
D/ 50
E/ 80

Let the rate of B be $$x$$ miles per hour, then the rate of A would be $$x+10$$ miles per hour.

We also know that the time of B equals to time of A + 2: $$\frac{400}{x}=\frac{400}{x+10}+2$$, from this point it's better to plug the answer choices rather than to solve the quadratics. You can quickly find that $$\frac{400}{40}=10=\frac{400}{40+10}+2=8+2$$

Hi Bunuel,
This question needs an edit.
The time it took car A to travel 400 miles was 2 hours less than the time it took car B to travel the same distance. If car A ‘s average speed was 10 mi greater than that of average speed of Car B , the what was Car B’s average speed in miles per hour?

Probus

_______________
Edited. Thank you.
_________________
Re: The time it took car A to travel 400 miles was 2 hours less than the &nbs [#permalink] 11 Aug 2018, 13:23
Display posts from previous: Sort by