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

 It is currently 18 Oct 2018, 02:24

### 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

# Tom traveled the entire 90 km trip. If he travelled the first 18 km of

Author Message
TAGS:

### Hide Tags

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6385
GMAT 1: 760 Q51 V42
GPA: 3.82
Tom traveled the entire 90 km trip. If he travelled the first 18 km of  [#permalink]

### Show Tags

27 Oct 2017, 01:32
00:00

Difficulty:

15% (low)

Question Stats:

87% (01:31) correct 13% (01:36) wrong based on 95 sessions

### HideShow timer Statistics

[GMAT math practice question]

Tom traveled the entire 90 km trip. If he travelled the first 18 km of the trip at a constant rate of 36 km per hour and the remaining trip at a constant rate of 72 km per hour, what is his average speed?

A. 30 km/h
B. 36 km/h
C. 45 km/h
D. 48 km/h
E. 60 km/h

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Senior PS Moderator Joined: 26 Feb 2016 Posts: 3185 Location: India GPA: 3.12 Tom traveled the entire 90 km trip. If he travelled the first 18 km of [#permalink] ### Show Tags 27 Oct 2017, 02:01 MathRevolution wrote: [GMAT math practice question] Tom traveled the entire 90 km trip. If he travelled the first 18 km of the trip at a constant rate of 36 km per hour and the remaining trip at a constant rate of 72 km per hour, what is his average speed? A. 30 km/h B. 36 km/h C. 45 km/h D. 48 km/h E. 60 km/h The formula for average speed is $$\frac{(p+q)(ab)}{(qa + pb)}$$ where distance is in the ratio p:q speed of travel in first leg is a, speed in second leg is b. From this question, we get the ratio of the distance to be 1:4(p:q) because he travels the first 18 kms at 36 km/hr and next 72 kms at 72 km/hr Substituting values, the average speed = $$\frac{(1+4)(36*72)}{(72*1 + 36*4)}$$ = $$\frac{5*36*72}{72(1+2)}$$ = 5*12 = 60(Option E) _________________ You've got what it takes, but it will take everything you've got Senior SC Moderator Joined: 22 May 2016 Posts: 2033 Tom traveled the entire 90 km trip. If he travelled the first 18 km of [#permalink] ### Show Tags 27 Oct 2017, 14:11 1 MathRevolution wrote: [GMAT math practice question] Tom traveled the entire 90 km trip. If he travelled the first 18 km of the trip at a constant rate of 36 km per hour and the remaining trip at a constant rate of 72 km per hour, what is his average speed? A. 30 km/h B. 36 km/h C. 45 km/h D. 48 km/h E. 60 km/h Average speed = $$\frac{TotalDistance}{TotalTime}$$ We need to find the time for each part of the trip (which requires easily finding distance for second part), add the times, and divide into total distance of 90. 1) TIME for Part 1 of trip? RT=D: He traveled 18 km at 36 km per hour. Distance/rate = time, so he took $$Time=\frac{D}{R}: \frac{18}{36}=\frac{1}{2}hr$$ 2) DISTANCE for Part 2? 90 km total, 18 km covered, means (90 - 18) = 72 km remain 3) TIME, Part 2? He traveled 72 km at a speed of 72 km per hour, so $$Time=\frac{D}{R}: \frac{72}{72}= 1 hr$$ 4) AVERAGE SPEED? Total distance = 90 km Total time: $$(\frac{1}{2} + 1)hrs = \frac{3}{2} hrs$$ Average speed in km per hr: $$\frac{90}{(\frac{3}{2})}=(90 * \frac{2}{3})=60$$ Answer E _________________ The only thing more dangerous than ignorance is arrogance. -- Albert Einstein Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 6385 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of [#permalink] ### Show Tags 29 Oct 2017, 18:06 => 90 / (18/36 + 72/72) = 90 / 1.5 = 60 Therefore, the answer is E. Answer: E _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Manager
Joined: 22 May 2015
Posts: 106
Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of  [#permalink]

### Show Tags

29 Oct 2017, 19:38
Avg speed = Total distance / total time = 90kms /( 0.5 hrs + 1 hr) = 60 kmph

Sent from my Moto G (5) Plus using GMAT Club Forum mobile app
_________________

Consistency is the Key

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4094
Location: India
GPA: 3.5
Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of  [#permalink]

### Show Tags

30 Oct 2017, 08:12
MathRevolution wrote:
[GMAT math practice question]

Tom traveled the entire 90 km trip. If he travelled the first 18 km of the trip at a constant rate of 36 km per hour and the remaining trip at a constant rate of 72 km per hour, what is his average speed?

A. 30 km/h
B. 36 km/h
C. 45 km/h
D. 48 km/h
E. 60 km/h

Distance covered in first half = 18 km , Speed = 36km/hr , Time = $$\frac{1}{2} Hr$$
Distance covered in second half = 72 km , Speed = 72 km/hr , Time = 1 Hr

Total time taken = $$\frac{3}{2} Hr$$

So, Average speed = $$\frac{90*2}{3}$$ = $$60 km/hr$$
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of  [#permalink]

### Show Tags

30 Oct 2017, 14:09
MathRevolution wrote:
[GMAT math practice question]

Tom traveled the entire 90 km trip. If he travelled the first 18 km of the trip at a constant rate of 36 km per hour and the remaining trip at a constant rate of 72 km per hour, what is his average speed?

A. 30 km/h
B. 36 km/h
C. 45 km/h
D. 48 km/h
E. 60 km/h

We can let the time for the first 18 km = 18/36 = 1/2 and the time for the rest of the trip = 72/72 = 1; thus:

average speed = (total distance)/(total time)

average speed = 90/(1/2 + 2) = 90/(3/2) = 60 km/h

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Manager
Joined: 07 Jun 2017
Posts: 174
Location: India
Concentration: Technology, General Management
GMAT 1: 660 Q46 V38
GPA: 3.6
WE: Information Technology (Computer Software)
Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of  [#permalink]

### Show Tags

05 Nov 2017, 22:00
average speed = (total distance)/(total time)

72/72 = 1hour
18/36 = 1/2 hour
total km = 90
total time = 1.5 hour
so 90/1.5 = 60 km/hr
_________________

Regards,
Naveen
email: nkmungila@gmail.com
Please press kudos if you like this post

Re: Tom traveled the entire 90 km trip. If he travelled the first 18 km of &nbs [#permalink] 05 Nov 2017, 22:00
Display posts from previous: Sort by