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

It is currently 20 Oct 2019, 04:24

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

An empty swimming pool with a capacity of 5,760 gallons is being fille

  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: 58434
An empty swimming pool with a capacity of 5,760 gallons is being fille  [#permalink]

Show Tags

New post 26 Sep 2018, 05:14
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

63% (02:20) correct 38% (03:12) wrong based on 46 sessions

HideShow timer Statistics

An empty swimming pool with a capacity of 5,760 gallons is being filled with a pipe at the rate of 12 gallons per minute. An empty pipe that has the capacity to empty (3/4)th of the pool in 9 hours is also in operation. If the pool is already half-filled, and if both the pipes are in operation simultaneously, how many hours would it take to fill the pool to its full capacity?

(A) 6
(B) 12
(C) 24
(D) 36
(E) 72

_________________
IESE School Moderator
avatar
S
Joined: 11 Nov 2017
Posts: 132
Location: Belgium
Concentration: Technology, Operations
GMAT 1: 670 Q47 V34
GMAT 2: 750 Q50 V41
GMAT 3: 750 Q50 V41
GPA: 2.5
WE: Engineering (Aerospace and Defense)
Re: An empty swimming pool with a capacity of 5,760 gallons is being fille  [#permalink]

Show Tags

New post 28 Sep 2018, 07:18
1
one pipe adds 12 galons per minute allowing it to fill up the pool in 480 minutes (5760 / 12) or 8 hours
the other pipe can drain the pool 3/4 in 9 hours --> drain the full pool in 12 hours
12 hours is 720 minutes meaning the galons per minute draining of this pipe is 8

there's no need to even do the division here since 8h x 12g/min = 12h x 8g/min
the number just change sides
so 1 pipe adds 12g while the other drains 8g meaning there's a net difference of 4g/min

since the pool is half full it's at 5760/2 = 2880g
and still needs 2880g to be filled

at 4g/min this means 720mins or 12hours

B

kudos if the explanation helped
Manager
Manager
avatar
G
Joined: 19 Apr 2017
Posts: 172
Concentration: General Management, Sustainability
Schools: ESSEC '22
GPA: 3.9
WE: Operations (Hospitality and Tourism)
Re: An empty swimming pool with a capacity of 5,760 gallons is being fille  [#permalink]

Show Tags

New post 28 Sep 2018, 07:29
1
Pool capacity = 5,760 gallons

Rate of incoming per hour = 12*60 gallons per hour=720
Rate of outgoing per hour = \((3/4)*(5760)*1/9=5760/12 = 480\)

Effective Rate = 720-480 = 240 per hour

If the pool is already half-filled it needs to fill 5760*1/2= 2880

Time taken to fill 2880 at the rate of 240 gallons per hour = 2880/240 = 12 hours
Director
Director
avatar
G
Joined: 09 Mar 2018
Posts: 994
Location: India
Re: An empty swimming pool with a capacity of 5,760 gallons is being fille  [#permalink]

Show Tags

New post 28 Sep 2018, 07:41
1
Basically we needed to find time (This approach is not time consuming just the explanation makes it look like one )

Work = Rate * Time

Time = Remaining Work/Combined Rate

Remaining work = 2880 G
Combined Rate = Ra - Rb

Ra - Rate of the inlet pipe
Rb - Rate of the outlet pipe

Converting the rates in minutes will be easy

Rb => 8 G/min
9 hours = 4320 G
1 hour = 480 G
1 min = 480/60 = 8 G/min

Ra => 12 G/min

Now
Time = 2880/(12-8)
Time = 720 mins

Convert this to hours 720/60 = 12 hours

Answer option B
_________________
If you notice any discrepancy in my reasoning, please let me know. Lets improve together.

Quote which i can relate to.
Many of life's failures happen with people who do not realize how close they were to success when they gave up.
GMAT Club Bot
Re: An empty swimming pool with a capacity of 5,760 gallons is being fille   [#permalink] 28 Sep 2018, 07:41
Display posts from previous: Sort by

An empty swimming pool with a capacity of 5,760 gallons is being fille

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





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