It is currently 17 Feb 2018, 16:43

### 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

# David travels one-third of the distance from LA to SF at a s

Author Message
TAGS:

### Hide Tags

Intern
Joined: 24 Jan 2014
Posts: 10
Schools: SMU Singapore
David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

08 Apr 2014, 07:24
2
KUDOS
1
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

71% (01:20) correct 29% (01:08) wrong based on 216 sessions

### HideShow timer Statistics

David travels one-third of the distance from LA to SF at a speed of 40 miles an hour and the balance at a speed of 80 miles an hour. What is the average speed of David's travel from LA to SF?

A. 66.67 miles per hour

B. 48 miles per hour

C. 64 miles per hour

D. 60 miles per hour

E. 53.33 miles per hour
[Reveal] Spoiler: OA

Last edited by Bunuel on 08 Apr 2014, 07:58, edited 1 time in total.
Renamed the topic and edited the tags.
Math Expert
Joined: 02 Sep 2009
Posts: 43789
Re: David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

08 Apr 2014, 08:06
1
KUDOS
Expert's post
Safal wrote:
David travels one-third of the distance from LA to SF at a speed of 40 miles an hour and the balance at a speed of 80 miles an hour. What is the average speed of David's travel from LA to SF?

A. 66.67 miles per hour

B. 48 miles per hour

C. 64 miles per hour

D. 60 miles per hour

E. 53.33 miles per hour

(Average speed) = (total distance)/(total time).

Say the distance from LA to SF is d miles, then (Average speed) = (total distance)/(total time) = $$\frac{d}{\frac{(\frac{d}{3})}{40}+\frac{(\frac{2d}{3})}{80}}=\frac{d}{\frac{d}{120}+\frac{d}{120}}=60$$ miles per hour.

Also, please tag the topics properly: this is a distance/rate problem, not arithmetic.

Thank you.

_________________
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1839
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

09 Apr 2014, 00:37
1
KUDOS
Lets say he travels total 3 Miles........ (1)

So, speed for 1 mile = 40
Speed for next 2 miles = 80

Total time taken $$=\frac{1}{40} + \frac{2}{80} = \frac{2}{40}$$........ (2)

$$Average = \frac{Total distance}{Total time}$$

$$= 3 * \frac{40}{2}$$

= 60

_________________

Kindly press "+1 Kudos" to appreciate

Non-Human User
Joined: 09 Sep 2013
Posts: 13845
Re: David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

15 Jun 2015, 06:30
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
SVP
Joined: 08 Jul 2010
Posts: 1950
Location: India
GMAT: INSIGHT
WE: Education (Education)
Re: David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

15 Jun 2015, 07:07
Safal wrote:
David travels one-third of the distance from LA to SF at a speed of 40 miles an hour and the balance at a speed of 80 miles an hour. What is the average speed of David's travel from LA to SF?

A. 66.67 miles per hour

B. 48 miles per hour

C. 64 miles per hour

D. 60 miles per hour

E. 53.33 miles per hour

Another way to solve the question is by assuming the distance which will avoid the unwanted calculation of fractions

Let's assume the distance which is divisible by 3 as 1/3 Distance is Travelled @40 mph
also Let's assume a distance that is divisible by 40 and 80 as well as TIME = DISTANCE/SPEED and Speeds are 40 and 80 mph

Let, Distance = 240 Miles

1/3 Distance = (1/3)*240 = 80 miles is Travelled @40 mph

i.e. TIME TAKEN = Distance / Speed = 80/40 = 2 hours

2/3 Distance = (2/3)*240 = 160 miles is Travelled @80 mph

i.e. TIME TAKEN = Distance / Speed = 160/80 = 2 hours

TOTAL DISTANCE = 240
TOTAL TIME = 2+2 = 4 Hours

AVERAGE SPEED = TOTAL DISTANCE / TOTAL TIME = 240/4 = 60 mph

[Reveal] Spoiler:
D

_________________

Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION

Non-Human User
Joined: 09 Sep 2013
Posts: 13845
Re: David travels one-third of the distance from LA to SF at a s [#permalink]

### Show Tags

26 Aug 2017, 15:06
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: David travels one-third of the distance from LA to SF at a s   [#permalink] 26 Aug 2017, 15:06
Display posts from previous: Sort by