• NEW! FREE Beat The GMAT Quizzes
Hundreds of Questions Highly Detailed Reporting Expert Explanations
• 7 CATs FREE!
If you earn 100 Forum Points

Engage in the Beat The GMAT forums to earn
100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote The speed of a boat is 5 times the speed at which a river fl tagged by: Max@Math Revolution This topic has 5 expert replies and 0 member replies GMAT/MBA Expert The speed of a boat is 5 times the speed at which a river fl Timer 00:00 Your Answer A B C D E Global Stats Difficult [Math Revolution GMAT math practice question] The speed of a boat is 5 times the speed at which a river flows. What percent of the time it takes for the boat to travel down the river (i.e. in the same direction as the river flow) does it take for the boat to travel up the river? A. 50% B. 80% C. 100% D. 150% E. 200% _________________ Math Revolution Finish GMAT Quant Section with 10 minutes to spare. The one-and-only Worldâ€™s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. Only$149 for 3 month Online Course
Free Resources-30 day online access & Diagnostic Test
Email to : info@mathrevolution.com

GMAT/MBA Expert

GMAT Instructor
Joined
09 Oct 2010
Posted:
1449 messages
Followed by:
32 members
59
Max@Math Revolution wrote:
[Math Revolution GMAT math practice question]

The speed of a boat is 5 times the speed at which a river flows. What percent of the time it takes for the boat to travel down the river (i.e. in the same direction as the river flow) does it take for the boat to travel up the river?

A. 50%
B. 80%
C. 100%
D. 150%
E. 200%
$$? = {{{T_{{\rm{up}}}}} \over {{T_{{\rm{down}}}}}}$$
$${V_r} = {{1\,\,{\rm{m}}} \over {1\,\,\sec }}\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{V_b} = {{5\,\,{\rm{m}}} \over {1\,\,\sec }}$$
$${\rm{distance}} = 12\,{\rm{m}}$$
$$\left. \matrix{ {\rm{down}}\,\,{\rm{:}}\,\,\,{\rm{12}}\,{\rm{m}}\,\,\left( {{{1\,\,\sec } \over {5 + 1\,\,{\rm{m}}}}} \right) = \,\,\,2\,\,\sec \,\,\, = \,\,\,{T_{{\rm{down}}}} \hfill \cr {\rm{up}}\,\,{\rm{:}}\,\,\,{\rm{12}}\,{\rm{m}}\,\,\left( {{{1\,\,\sec } \over {5 - 1\,\,{\rm{m}}}}} \right) = \,\,\,3\,\,\sec \,\,\, = \,\,\,{T_{{\rm{up}}}} \hfill \cr} \right\}\,\,\,\,\, \Rightarrow \,\,\,\,\,? = \,\,{3 \over 2}\,\, = \,\,150\%$$

This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.

_________________
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br

GMAT/MBA Expert

GMAT Instructor
Joined
08 Dec 2008
Posted:
12827 messages
Followed by:
1247 members
5254
GMAT Score:
770
Max@Math Revolution wrote:
[Math Revolution GMAT math practice question]

The speed of a boat is 5 times the speed at which a river flows. What percent of the time it takes for the boat to travel down the river (i.e. in the same direction as the river flow) does it take for the boat to travel up the river?

A. 50%
B. 80%
C. 100%
D. 150%
E. 200%
Let x = the speed of the river (in miles per hour)
So, 5x = the speed of the boat in (miles per hour)
Let d = distance traveled (in miles)

This means the boat's speed going UPriver = 5x - x = 4x
And the boat's speed going DOWNriver = x + 5x = 6x

time = distance/speed
So, travel time going UPriver = d/4x
So, travel time going DOWNriver = d/6x

What percent of the time it takes for the boat to travel DOWNriver does it take for the boat to travel UPriver?
We must take the fraction (d/4x)/(d/6x), and convert it to a PERCENT

(d/4x)/(d/6x) = (d/4x)(6x/d)
= 6xd/4xd
= 6/4
= 3/2
= 150/100
= 150%

Cheers,
Brent

_________________
Brent Hanneson â€“ Creator of GMATPrepNow.com
Use our video course along with

And check out all of our free resources

GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™s FREE 60-Day Study Guide and reach your target score in 2 months!

GMAT/MBA Expert

GMAT Instructor
Joined
25 May 2010
Posted:
15254 messages
Followed by:
1861 members
13060
GMAT Score:
790
Max@Math Revolution wrote:
[Math Revolution GMAT math practice question]

The speed of a boat is 5 times the speed at which a river flows. What percent of the time it takes for the boat to travel down the river (i.e. in the same direction as the river flow) does it take for the boat to travel up the river?

A. 50%
B. 80%
C. 100%
D. 150%
E. 200%
Let the river's rate = 1 mph and the boat's rate = 5 mph.

When the boat travels DOWNRIVER, the boat and the river WORK TOGETHER, so we ADD their rates:
5+1 = 6 mph.
When the boat travels UPRIVER, the boat and the river COMPETE, so we SUBTRACT their rates:
5-1 = 4 mph.

Rate and time have a RECIPROCAL relationship.
Since the rate upriver is 4/6 of the rate downriver, the time upriver is 6/4 of the time downriver:
6/4 * 100 = 150%.

_________________
Mitch Hunt
Private Tutor for the GMAT and GRE
GMATGuruNY@gmail.com

If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.

Available for tutoring in NYC and long-distance.
Student Review #1
Student Review #2
Student Review #3

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

GMAT/MBA Expert

Legendary Member
Joined
24 Jul 2015
Posted:
2219 messages
Followed by:
32 members
19
GMAT Score:
=>

Let d and v be the distance the boat travels and the speed of the river flow, respectively.
The time the boat takes to travel up the river is d / ( 5v - v ) = d/4v.
The time the boat takes to travel down the river is d / ( 5v + v ) = d/6v.
Let p be the percentage are looking for.
Using the IVY approach, we obtain d/4v = p(1/100)(d/6v) or p = (6/4)*100 = 150(%).

_________________

Math Revolution
Finish GMAT Quant Section with 10 minutes to spare.
The one-and-only Worldâ€™s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Only $149 for 3 month Online Course Free Resources-30 day online access & Diagnostic Test Unlimited Access to over 120 free video lessons-try it yourself Email to : info@mathrevolution.com GMAT/MBA Expert GMAT Instructor Joined 25 Apr 2015 Posted: 2424 messages Followed by: 18 members Upvotes: 43 Max@Math Revolution wrote: [Math Revolution GMAT math practice question] The speed of a boat is 5 times the speed at which a river flows. What percent of the time it takes for the boat to travel down the river (i.e. in the same direction as the river flow) does it take for the boat to travel up the river? A. 50% B. 80% C. 100% D. 150% E. 200% We can let the current of the river be 2 mph. Thus the speed of the boat is 5 x 2 = 10 mph. Furthermore, when the boat travels with the current, its speed is 10 + 2 = 12 mph, but when it travels against the current, its speed is 10 - 2 = 8 mph. Letâ€™s let the length of the river be 24 miles. It will take the boat 24/12 = 2 hours when it travels with the current and 24/8 = 3 hours when it travels against the current. Therefore, the time it takes for the boat to travel up the river (i.e., against the current) is 3/2 = 150% of the time it takes for the boat to travel down the river (i.e., with the current). Answer: D _________________ Scott Woodbury-Stewart Founder and CEO scott@targettestprep.com See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews • Free Veritas GMAT Class Experience Lesson 1 Live Free Available with Beat the GMAT members only code • Free Trial & Practice Exam BEAT THE GMAT EXCLUSIVE Available with Beat the GMAT members only code • FREE GMAT Exam Know how you'd score today for$0

Available with Beat the GMAT members only code

• Get 300+ Practice Questions

Available with Beat the GMAT members only code

• Award-winning private GMAT tutoring
Register now and save up to \$200

Available with Beat the GMAT members only code

• 5-Day Free Trial
5-day free, full-access trial TTP Quant

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

Top First Responders*

1 Jay@ManhattanReview 71 first replies
2 Brent@GMATPrepNow 67 first replies
3 GMATGuruNY 43 first replies
4 Ian Stewart 27 first replies
5 Scott@TargetTestPrep 18 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 Scott@TargetTestPrep

Target Test Prep

221 posts
2 Max@Math Revolution

Math Revolution

93 posts
3 Brent@GMATPrepNow

GMAT Prep Now Teacher

90 posts
4 Jay@ManhattanReview

Manhattan Review

73 posts
5 GMATGuruNY

The Princeton Review Teacher

66 posts
See More Top Beat The GMAT Experts