GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 01 Jun 2020, 05:20

### 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

# M15-32

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 64150

### Show Tags

15 Sep 2014, 23:57
00:00

Difficulty:

55% (hard)

Question Stats:

69% (02:09) correct 31% (01:42) wrong based on 84 sessions

### HideShow timer Statistics

If a car went the first third of the distance at 80 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

A. 36 kmh
B. 40 kmh
C. 42 kmh
D. 44 kmh
E. 50 kmh

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 64150

### Show Tags

15 Sep 2014, 23:57
1
4
Official Solution:

If a car went the first third of the distance at 80 kmh, the second third at 24 kmh, and the last third at 48 kmh, what was the average speed of the car for the entire trip?

A. 36 kmh
B. 40 kmh
C. 42 kmh
D. 44 kmh
E. 50 kmh

Say the total distance is $$3x$$ kilometers, then: $$total \ time=\frac{x}{80}+\frac{x}{24}+\frac{x}{48}=\frac{18x}{240}$$;

$$Average \ speed=\frac{total \ distance}{total \ time}=\frac{3x}{\frac{18x}{240}}=\frac{240*3}{18}=40$$.

_________________
##### General Discussion
Intern
Joined: 15 Feb 2018
Posts: 1

### Show Tags

24 Feb 2018, 08:58
I think this is a high quality question, thanks
Intern
Status: Current Student
Joined: 26 Mar 2014
Posts: 26
Concentration: Entrepreneurship, Finance

### Show Tags

24 Feb 2018, 17:41
1
$$Rate*time=distance$$
So, $$80*t=\frac{1}{3} => t1=\frac{1}{3}*80$$
Similarly, $$t2=\frac{1}{3}*24$$ and $$t3=\frac{1}{3}*48$$
So, total time= $$t1+t2+t3 = \frac{1}{3}(\frac{1}{80}+\frac{1}{24}+\frac{1}{48}) = \frac{1}{3}*\frac{1}{8}(\frac{1}{10}+\frac{1}{3}+\frac{1}{6}) = \frac{1}{24}*\frac{18}{30} = \frac{1}{40}$$
Average speed = $$\frac{(total distance)}{(total time)}= \frac{1}{1/40}$$ = 40 kph
M15-32   [#permalink] 24 Feb 2018, 17:41

# M15-32

Moderators: chetan2u, Bunuel