GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 24 Jan 2019, 02:52

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

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

Events & Promotions

Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
• Key Strategies to Master GMAT SC

January 26, 2019

January 26, 2019

07:00 AM PST

09:00 AM PST

Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
• Free GMAT Number Properties Webinar

January 27, 2019

January 27, 2019

07:00 AM PST

09:00 AM PST

Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes.

One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3

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

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 52452
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3  [#permalink]

Show Tags

20 Mar 2018, 22:03
00:00

Difficulty:

15% (low)

Question Stats:

94% (01:48) correct 6% (04:07) wrong based on 83 sessions

HideShow timer Statistics

One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 hours. A second inlet pipe can fill the empty cistern to 3/4 of its capacity in 4.5 hours. If both pipes are opened simultaneously, how long, in hours, will it take to fill the cistern?

(A) 4.75
(B) 4.25
(C) 3.75
(D) 3.6
(E) 3.25

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 52452
Re: One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3  [#permalink]

Show Tags

20 Mar 2018, 22:04
Bunuel wrote:
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 hours. A second inlet pipe can fill the empty cistern to 3/4 of its capacity in 4.5 hours. If both pipes are opened simultaneously, how long, in hours, will it take to fill the cistern?

(A) 4.75
(B) 4.25
(C) 3.75
(D) 3.6
(E) 3.25

17. Work/Rate Problems

On other subjects:
ALL YOU NEED FOR QUANT ! ! !
Ultimate GMAT Quantitative Megathread
_________________
Senior PS Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 680
Re: One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3  [#permalink]

Show Tags

21 Mar 2018, 00:00
Bunuel wrote:
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 hours. A second inlet pipe can fill the empty cistern to 3/4 of its capacity in 4.5 hours. If both pipes are opened simultaneously, how long, in hours, will it take to fill the cistern?

(A) 4.75
(B) 4.25
(C) 3.75
(D) 3.6
(E) 3.25

IMO D.

First pipe fills 1/3rd cistern in 3 hours. So whole cistern in 9 hours. Therefor it's rate = 1/9 cistern per hour.
Second pipe fills 3/4th cistern in 4.5 hours.

So it fills 1 cistern in 4.5 * 4/3 = 6 hours. Rate of second pipe = 1/6 cistern per hour

When working together rates will add up.

together rate = 1/6 + 1/9
=3/18 + 2/18
=5/18 cistern in one hour

Hence 1 cistern in 18/5 hours or 3.6 hrs

Hence Option D.

Best,
_________________

Regards,

“Do. Or do not. There is no try.” - Yoda (The Empire Strikes Back)

Senior SC Moderator
Joined: 22 May 2016
Posts: 2376
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3  [#permalink]

Show Tags

23 Mar 2018, 21:33
Bunuel wrote:
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 hours. A second inlet pipe can fill the empty cistern to 3/4 of its capacity in 4.5 hours. If both pipes are opened simultaneously, how long, in hours, will it take to fill the cistern?

(A) 4.75
(B) 4.25
(C) 3.75
(D) 3.6
(E) 3.25

Pipe 1 rate: $$\frac{(\frac{1}{3})}{3}=(\frac{1}{3}*\frac{1}{3})=\frac{1}{9}$$

Pipe 2 rate: $$\frac{\frac{3}{4}}{\frac{9}{2}}=(\frac{3}{4}*\frac{2}{9})=\frac{1}{6}$$

Together, combined rate is
$$(\frac{1}{9}+\frac{1}{6})=\frac{15}{54}=\frac{5}{18}$$

W = 1 (cistern)
Rate and time are inversely proportional, and here, multiplied, they must equal 1.

Flip the rate to get the time, in hours, that it would take to fill the cistern*:
$$\frac{18}{5}= 3.6$$ hours

*OR
$$R*T = W$$, so $$T=\frac{W}{R}$$
$$T = \frac{1}{(\frac{5}{18})}= (1* \frac{18}{5})=3.6$$ hours

_________________

Sometimes at night I would sleep open-eyed underneath a sky dripping with stars.
I was alive then.

—Albert Camus

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4354
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
Re: One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3  [#permalink]

Show Tags

24 Mar 2018, 06:43
Bunuel wrote:
One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 hours. A second inlet pipe can fill the empty cistern to 3/4 of its capacity in 4.5 hours. If both pipes are opened simultaneously, how long, in hours, will it take to fill the cistern?

(A) 4.75
(B) 4.25
(C) 3.75
(D) 3.6
(E) 3.25
First inlet pipe can fill the empty cistern in 9 hours and the second inlet pipe can fill the cistern in 6 hours.

Let the total capacity of the Cistern be 18 units.

So, Efficiency of the First Inlet pipe is 2 units/hour and efficiency of the Second inlet pipe is 3 units/hour

Combined efficiency of both the pipes is 5 units /hour, thus working together the 2 machines can fill the cistern in $$\frac{18}{5}$$ = $$3.6$$ hours, Answer must be (D)
_________________

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 )

Re: One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3 &nbs [#permalink] 24 Mar 2018, 06:43
Display posts from previous: Sort by

One inlet pipe can fill an empty cistern to 1/3 of its capacity in 3

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.