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 Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Susan drove an average speed of 30 miles per hour for the [#permalink]

Show Tags

02 Nov 2010, 06:56

5

This post received KUDOS

12

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

5% (low)

Question Stats:

76% (00:36) correct
24% (00:35) wrong based on 857 sessions

HideShow timer Statistics

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip and then at an average speed of 60 miles per hour for the remaining 30 miles of the trip. If she made no stops during the trip, what was Susan's average speed, in miles per hour, for the entire trip?

a. 35 b. 40 c. 45 d. 50 e. 55

The Common Formula is Average speed = Total distance / Total time. However if the distances traveled with two different speeds are the same (as 30 in this case), we can calculate the average speed as per following rule. ratio of two distinct speeds = 1:2 Difference of two distinct speeds = 60 - 30 = 30 Now divide this difference by the sum of intergers of ratio (i.e. by 1+2 = 3 in this case ) 30/3 = 10 Average speed will be 10 X 1 part away from the lower speed i.e. 30 + 10 X 1 = 40.

The benefit of this method is once practiced enough you can calculate the average speed mentally or with minimal calculation and thereby can save valuable time on the GMAT

Re: Susan drove an average speed of 30 miles per hour for the [#permalink]

Show Tags

30 Jul 2013, 16:45

1

This post received KUDOS

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

What we have here are equal distances for both segments.

First segment: 30 miles/hour and covered 30 miles, therefore it took one hour. Second segment: 60 miles/hour and covered 30 miles, therefore it took 1/2 hour.

(Total distance / total time) (60 / [1hr+ 1/2hr]) (60 / 1.5) = 40 miles avg. speed.

A. 35 B. 40 C. 45 D. 50 E. 55

(B)

When don't we simply add the distances/speeds together to get the average?

Re: Susan drove an average speed of 30 miles per hour for the [#permalink]

Show Tags

10 Feb 2016, 21:17

Narenn wrote:

jsphcal wrote:

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip and then at an average speed of 60 miles per hour for the remaining 30 miles of the trip. If she made no stops during the trip, what was Susan's average speed, in miles per hour, for the entire trip?

a. 35 b. 40 c. 45 d. 50 e. 55

The Common Formula is Average speed = Total distance / Total time. However if the distances traveled with two different speeds are the same (as 30 in this case), we can calculate the average speed as per following rule. ratio of two distinct speeds = 1:2 Difference of two distinct speeds = 60 - 30 = 30 Now divide this difference by the sum of intergers of ratio (i.e. by 1+2 = 3 in this case ) 30/3 = 10 Average speed will be 10 X 1 part away from the lower speed i.e. 30 + 10 X 1 = 40.

The benefit of this method is once practiced enough you can calculate the average speed mentally or with minimal calculation and thereby can save valuable time on the GMAT

Regards,

Abhijit

Nice method, but why should it be 10 away from the lower speed and not from the higher speed?

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

A. 35 B. 40 C. 45 D. 50 E. 55

We are given that Susan drove at an average speed of 30 miles per hour for the first 30 miles of a trip and then at an average speed of 60 miles per hour for the remaining 30 miles of the trip. We must determine her average speed overall. The formula for average speed is:

average speed = total distance/total time

For the first half of the trip, we know that Susan’s speed was 30 mph and her distance was 30 miles, so her time was 30/30 = 1 hour.

For the second half of the trip, we know that Susan’s speed was 60 mph and her distance was 30 miles, so her time was 30/60 = 1/2 hour. Therefore her average speed in miles per hour is:

average speed = (30 + 30)/(1 + ½)

average speed = 60/(3/2)

average speed = 40

Answer: B
_________________

Scott Woodbury-Stewart Founder and CEO

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

Re: Susan drove an average speed of 30 miles per hour for the [#permalink]

Show Tags

11 May 2017, 05:03

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

A. 35 B. 40 C. 45 D. 50 E. 55

Sol: Average Speed = Total Distance/Total time Total Distance = 30 miles + 30 miles = 60 miles Total time = Time taken for the 1st 30 miles + time taken for the next 30 miles = (30miles/30mph) + (30 miles/60 mph) = (1 + 0.5) hours = 1.5 hours

Average speed = Total Distance/Total time = 60/1.5 = 40 mph The answer is (B).
_________________

Concentration: General Management, Entrepreneurship

GPA: 3.8

WE: Engineering (Energy and Utilities)

Re: Susan drove an average speed of 30 miles per hour for the [#permalink]

Show Tags

11 May 2017, 05:12

anilnandyala wrote:

Susan drove an average speed of 30 miles per hour for the first 30 miles of a trip & then at a average speed of 60 miles/hr for the remaining 30 miles of the trip if she made no stops during the trip what was susan's avg speed in miles/hr for the entire trip

A. 35 B. 40 C. 45 D. 50 E. 55

Time taken in travelling 1st 30 miles = 30/30 = 1 hr Time taken in travelling remaining 30 miles = 30/60 = 1/2 hr Total distance traveled = 30+30 = 60 miles Total time taken = 1+1/2 = 3/2 hr Average speed = \(\frac{60}{(3/2)}\) = 40 miles/hr
_________________

Version 8.1 of the WordPress for Android app is now available, with some great enhancements to publishing: background media uploading. Adding images to a post or page? Now...

Post today is short and sweet for my MBA batchmates! We survived Foundations term, and tomorrow's the start of our Term 1! I'm sharing my pre-MBA notes...

“Keep your head down, and work hard. Don’t attract any attention. You should be grateful to be here.” Why do we keep quiet? Being an immigrant is a constant...