A boat traveled upstream a distance of 90 miles at avg speed of (v-3) miles per hour and than traveled the same distance downstream at an avg speed of (v+3)miles per hr.If the trip upstream took half an hour longer than the trip downstream . How many hours did it take the boat to travel downstream??
Appreciate yr help!!
Thanks!!
Boat
This topic has expert replies
GMAT/MBA Expert
- Anurag@Gurome
- GMAT Instructor
- Posts: 3835
- Joined: Fri Apr 02, 2010 10:00 pm
- Location: Milpitas, CA
- Thanked: 1854 times
- Followed by:523 members
- GMAT Score:770
Time taken to travel upstream = 90/(v - 3) hrAshetty wrote:A boat traveled upstream a distance of 90 miles at avg speed of (v-3) miles per hour and than traveled the same distance downstream at an avg speed of (v+3)miles per hr.If the trip upstream took half an hour longer than the trip downstream . How many hours did it take the boat to travel downstream??
Appreciate yr help!!
Thanks!!
Time taken to travel downstream = 90/(v + 3) hr
Traveling upstream took 1/2hr more than downstream.
So, 90/(v - 3) = 90/(v + 3) + 1/2
180(v + 3) = 180(v - 3) + (v² - 9)
1080 = v² - 9 or v = √1089 = 33
Speed for downstream = 33 + 3 = 36 mph
Therefore, time taken to travel downstream = 90/36 = 2.5 hrs
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
We can plug in the answers, which represent the number of hours that the boat took to travel downstream.A boat traveled upstream a distance of 90 miles at an average speed of (V-3) miles per hour and then travelled the same distance downstream at an average speed of (V+3) miles per hour.If the trip upstream half an hour longer than downstream, how many hours did it take the boat to travel downstream?
(*) 2.5
(*) 2.4
(*) 2.3
(*) 2.2
(*) 2.1
Since the trip upstream took 1/2 hour longer, the OA almost certainly is A -- the only answer choice that divides evenly into 90.
Answer choice A: 2.5 hours to travel downstream.
Rate downstream = d/t = 90/(2.5) = 36 hours.
Thus, v+3 = 36, implying that v=33.
Rate upstream = v-3 = 33-3 = 30 miles per hour.
Time upstream = d/r = 90/30 = 3 hours.
Time upstream - time downstream = 3-2.5 = .5.
Success!
The correct answer is A.
Please note the following:
-- Because we assessed the viability of the answer choices BEFORE we started to plug in, we had to try only ONE answer choice.
-- Plugging in the answers enabled us to determine the correct answer -- quickly and efficiently -- without having to set up and solve a quadratic equation.
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
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