GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

It is currently 29 Feb 2020, 03:04

Close

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
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.

Close

Request Expert Reply

Confirm Cancel

A motorboat went down the river for 14 km and then up the river for 9

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 61537
A motorboat went down the river for 14 km and then up the river for 9  [#permalink]

Show Tags

New post 03 Jan 2020, 01:29
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

78% (02:20) correct 22% (03:26) wrong based on 23 sessions

HideShow timer Statistics

Manager
Manager
avatar
G
Joined: 20 Aug 2017
Posts: 105
Premium Member
Re: A motorboat went down the river for 14 km and then up the river for 9  [#permalink]

Show Tags

New post 03 Jan 2020, 03:00
We are given the speed of boat as 5kmph and let speed of stream = X.
Now, we are given
\(\frac{14}{5+X} + \frac{9}{5-X} = 5\)
As we can see if we go on to solve the equation it will take a lot of time.
So we use options.
Option A: X = 1
Our equation becomes
\(\frac{14}{6} + \frac{9}{4} = 5\)

Now, \(\frac{14}{6}\) results in a non terminating decimal. Eliminated

Option B: X = 1.5
Our equation becomes
\(\frac{14}{6.5} + \frac{9}{3.5} = 5\)

\(\frac{140}{65} + \frac{90}{35} = 5\)

\(\frac{28}{13} + \frac{18}{7} = 5\)
This too will result in non terminating decimals. Eliminated

Option C: X = 2
Our equation becomes
\(\frac{14}{7} + \frac{9}{3} = 5\)

\(2+3 = 5\)
Hence, this becomes our answer.

We do not need to check further options.

OA, C

Bunuel wrote:
A motorboat went down the river for 14 km and then up the river for 9 km. It took a total of 5 hours for the entire journey. Find the speed of the river flow if the speed of the boat in still water is 5 kmph.

A. 1 kmph
B. 1.5 kmph
C. 2 kmph
D. 2.5 kmph
E. 3 kmph
Board of Directors
User avatar
D
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4848
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: A motorboat went down the river for 14 km and then up the river for 9  [#permalink]

Show Tags

New post 03 Jan 2020, 05:53
Bunuel wrote:
A motorboat went down the river for 14 km and then up the river for 9 km. It took a total of 5 hours for the entire journey. Find the speed of the river flow if the speed of the boat in still water is 5 kmph.

A. 1 kmph
B. 1.5 kmph
C. 2 kmph
D. 2.5 kmph
E. 3 kmph


Plugging in the options can work good for this one, the main equation is -

\(\frac{14}{5 + c} + \frac{9}{5 - c} = 5\)

Use option (C) 2

\(\frac{14}{5 + 2} + \frac{9}{5 - 2}\)

= \(\frac{14}{7} + \frac{9}{3}\)

= \(2 + 3\)

= \(5\) , Answer must hence be (C)
_________________
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 )
Senior Manager
Senior Manager
User avatar
G
Joined: 12 Sep 2017
Posts: 312
Re: A motorboat went down the river for 14 km and then up the river for 9  [#permalink]

Show Tags

New post 09 Jan 2020, 18:07
Hello uchihaitachi

Why did you get 5-X and 5+X?

Kind regards!
Manager
Manager
avatar
G
Joined: 20 Aug 2017
Posts: 105
Premium Member
Re: A motorboat went down the river for 14 km and then up the river for 9  [#permalink]

Show Tags

New post 09 Jan 2020, 19:09
It is the speed upstream and downstream.
The downstream speed = 5 + X
The upstream speed = 5 - X

jfranciscocuencag wrote:
Hello uchihaitachi

Why did you get 5-X and 5+X?

Kind regards!


Posted from my mobile device
GMAT Club Bot
Re: A motorboat went down the river for 14 km and then up the river for 9   [#permalink] 09 Jan 2020, 19:09
Display posts from previous: Sort by

A motorboat went down the river for 14 km and then up the river for 9

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne