Steve traveled the first 2 hours of his journey...

Expert replies

BTGmoderatorLU: Moderator; Posts: 2550; Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members

by BTGmoderatorLU » Wed Mar 07, 2018 2:19 pm

Steve traveled the first 2 hours of his journey at 40 mph and the remaining 3 hours of his journey at 80 mph. What is his average speed for the entire journey?

A. 60 mph
B. 56.67 mph
C. 53.33 mph
D. 64 mph
E. 66.67 mph

The OA is D.

I'm confused by this PS question. Experts, any suggestion, please? Thanks in advance.

Like this post

Source: Beat The GMAT — Problem Solving | Wed Mar 07, 2018 2:19 pm

mbawisdom: Senior | Next Rank: 100 Posts; Posts: 94; Joined: Tue Dec 16, 2014 9:50 amFollowed by: 4 members; Location: London, UK; Thanked: 2 times; GMAT Score:770

by mbawisdom » Wed Mar 07, 2018 2:57 pm

LUANDATO wrote:Steve traveled the first 2 hours of his journey at 40 mph and the remaining 3 hours of his journey at 80 mph. What is his average speed for the entire journey?

A. 60 mph
B. 56.67 mph
C. 53.33 mph
D. 64 mph
E. 66.67 mph

The OA is D.

I'm confused by this PS question. Experts, any suggestion, please? Thanks in advance.

Speed = Distance/Time
OR
Distance = Speed * Time

Part 1: D1 = 40*2 = 80

Part 2: D2 = 80*3 = 240

Total Distance = D1 + D2 = 80 + 240 = 320
Total Time = 2 + 3 = 5

Speed = 320/5 = 64 mph

Answer is D

Like this post

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Thu Mar 08, 2018 3:33 am

LUANDATO wrote:Steve traveled the first 2 hours of his journey at 40 mph and the remaining 3 hours of his journey at 80 mph. What is his average speed for the entire journey?

A. 60 mph
B. 56.67 mph
C. 53.33 mph
D. 64 mph
E. 66.67 mph

2 hours are spent at 40mph.
3 hours are spent at 80mph.
Average speed for all 5 hours = (2*40 + 3*80)/5 = 320/5 = 64.

The correct answer is D.

Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

Like this post

DavidG@VeritasPrep: Legendary Member; Posts: 2663; Joined: Wed Jan 14, 2015 8:25 amFollowed by: 128 members; Location: Boston, MA; Thanked: 1153 times; GMAT Score:770

by DavidG@VeritasPrep » Thu Mar 08, 2018 12:12 pm

LUANDATO wrote:Steve traveled the first 2 hours of his journey at 40 mph and the remaining 3 hours of his journey at 80 mph. What is his average speed for the entire journey?

A. 60 mph
B. 56.67 mph
C. 53.33 mph
D. 64 mph
E. 66.67 mph

The OA is D.

I'm confused by this PS question. Experts, any suggestion, please? Thanks in advance.

Mitch's and Dan's approach is probably simplest. But here's a fun alternative:

If Steve had spent the same amount of time traveling at each speed, his average would have been right in the middle of 40 and 80, or 60mph. We know he spent more time traveling at the faster speed, and thus, his average must be more than 60. That leaves us D and E.

Now we can test one of the two remaining choices and see if we get a 3:2 ratio in favor of time spent traveling at 80mph.
Test D: 64
Plot the rates on a number line:
40-----------------64-----------80
Gaps:-------24----------16--------
Ratio of time spent at 80 mph to 40 mph: 24:16 = 3:2. And we've got our answer.

Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course

Like this post

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8151; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Thu Jun 06, 2019 5:06 pm

BTGmoderatorLU wrote:Steve traveled the first 2 hours of his journey at 40 mph and the remaining 3 hours of his journey at 80 mph. What is his average speed for the entire journey?

A. 60 mph
B. 56.67 mph
C. 53.33 mph
D. 64 mph
E. 66.67 mph

Steve's total distance was 2 x 40 + 3 x 80 = 80 + 240 = 320 miles.

We can now determine average speed:

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

Average speed = 320/5 = 64 mph

Answer: D

Scott Woodbury-Stewart
Founder and CEO
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review