Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 25 May 2016, 15:01

### 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 June
Open Detailed Calendar

# A car travels from point A to point B. The average speed

Author Message
TAGS:

### Hide Tags

Manager
Joined: 18 Jun 2011
Posts: 58
Followers: 1

Kudos [?]: 98 [0], given: 0

A car travels from point A to point B. The average speed [#permalink]

### Show Tags

18 Jun 2011, 04:32
2
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

72% (02:15) correct 28% (01:09) wrong based on 107 sessions

### HideShow timer Statistics

A car travels from point A to point B. The average speed of the car is 60 miles/hr and it travels the first half of the trip at a speed of 90 mi/hr. What is the speed of the car in the second half of the trip?

A. 30
B. 45
C. 60
D. 75
E. 90

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-car-travels-from-point-a-to-point-b-the-average-speed-of-98076.html
[Reveal] Spoiler: OA
Senior Manager
Joined: 03 Mar 2010
Posts: 440
Schools: Simon '16 (M)
Followers: 5

Kudos [?]: 220 [1] , given: 22

### Show Tags

18 Jun 2011, 05:19
1
KUDOS
Avg Speed = Total Distance / Total time.

Let total distance = d
Let the speed of the car in the second half of the trip = S
Time taken to travel first half (d/2) at speed of 90m/hr t1= d/2*90 = d/180
Time taken to travel second half (d/2) at speed of s m/hr t2= d/2*s = d/2s

Total time = t1+t2 = d/180 + d/2s

Avg Speed = Total Distance / Total time.
60 = d/(t1+t2)
$$60=d/[(d/180) + d/2s)]$$
60 = 360s/(2s+180)
s=45

OA B.
_________________

My dad once said to me: Son, nothing succeeds like success.

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2022
Followers: 154

Kudos [?]: 1436 [0], given: 376

### Show Tags

18 Jun 2011, 06:18
guygmat wrote:
A car travels from point A to point B. The average speed of the car is 60 miles/hr and it travels the first half of the trip at a speed of 90 mi/hr. What is the speed of the car in the second half of the trip?

A)30
B)45
C)60
D)75
E)90

By weighted average:

Let the speed be S;

$$\frac{\frac{1}{S}-\frac{1}{60}}{\frac{1}{60}-\frac{1}{90}}=\frac{x}{x}=1$$

Upon solving;
S=45 m/h

Ans: "B"
_________________
Current Student
Joined: 26 May 2005
Posts: 565
Followers: 18

Kudos [?]: 181 [0], given: 13

### Show Tags

18 Jun 2011, 08:11
guygmat wrote:
A car travels from point A to point B. The average speed of the car is 60 miles/hr and it travels the first half of the trip at a speed of 90 mi/hr. What is the speed of the car in the second half of the trip?

A)30
B)45
C)60
D)75
E)90

Avg speed formula = 2XY/(x+Y)

2X*90/x+90 = 60
180X= 60X+5400
120X= 5400
X= 45.
B
Director
Joined: 29 Nov 2012
Posts: 900
Followers: 12

Kudos [?]: 791 [0], given: 543

### Show Tags

23 May 2013, 07:56
Great explanations this question was really tricky!
_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Math Expert
Joined: 02 Sep 2009
Posts: 32992
Followers: 5751

Kudos [?]: 70476 [0], given: 9847

Re: A car travels from point A to point B. The average speed [#permalink]

### Show Tags

23 May 2013, 09:29
Expert's post
2
This post was
BOOKMARKED
A car travels from point A to point B. The average speed of the car is 60 miles/hr and it travels the first half of the trip at a speed of 90 mi/hr. What is the speed of the car in the second half of the trip?

A. 30
B. 45
C. 60
D. 75
E. 90

Let the average speed for the second half of the trip be $$x$$ miles per hour.

Pick some smart number for the distance from A to B: let the distance be 180 miles, so half of the distance will be 90 miles.

$$Average \ speed=\frac{total \ distance}{total \ time}$$ --> $$60=\frac{180}{total \ time}$$;

Total time equals time for the first half plus time for the second half --> $$\frac{90}{90}+\frac{90}{x}=\frac{x+90}{x}$$;

So $$60=\frac{180}{total \ time}$$ --> $$60=\frac{180x}{x+90}$$ --> $$60x+60*90=180x$$ --> $$120x=60*90$$ --> $$x=45$$.

OPEN DISCUSSION OF THIS QUESTION IS HERE: a-car-travels-from-point-a-to-point-b-the-average-speed-of-98076.html
_________________
Re: A car travels from point A to point B. The average speed   [#permalink] 23 May 2013, 09:29
Similar topics Replies Last post
Similar
Topics:
7 Noelle walks from point A to point B at an average speed of 5 kilomete 7 19 Feb 2015, 09:43
7 A train travels from city A to city B. The average speed of the train 2 04 Nov 2014, 00:03
9 A car travels from Town A to Town B at an average speed 3 05 Jan 2013, 18:08
38 A car travels from point A to point B. The average speed of 18 26 Jul 2010, 22:46
8 A car travels from Mayville to Rome at an average speed of 3 9 18 Jul 2010, 10:53
Display posts from previous: Sort by