Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 25 Apr 2015, 08:11

### 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 June
Open Detailed Calendar

# A pool has two inlet pipes. The first inlet can fill the

Author Message
TAGS:
Director
Joined: 20 Aug 2007
Posts: 852
Location: Chicago
Schools: Chicago Booth 2011
Followers: 11

Kudos [?]: 87 [1] , given: 1

A pool has two inlet pipes. The first inlet can fill the [#permalink]  27 Feb 2008, 18:10
1
KUDOS
A pool has two inlet pipes. The first inlet can fill the pool in 6 hours, the other can fill it in 4 hours. If the first pipe is open for 2 hours and then the second is open. How long will take for the pool to be filled after the second pipe is open?
Intern
Joined: 25 Feb 2008
Posts: 14
Followers: 0

Kudos [?]: 1 [0], given: 0

Re: Rate problem [#permalink]  27 Feb 2008, 19:38
first inlet fills 1/3 after 2 hours. To fill = 2/3rds.
new effective rate = (6*4)/(6+4) = 2.4
if 100% = 2.4 what is (100 * 2/3)% = ?

= 2.4 * 2 /3 = 1.6 hours
SVP
Joined: 04 May 2006
Posts: 1936
Schools: CBS, Kellogg
Followers: 19

Kudos [?]: 433 [1] , given: 1

Re: Rate problem [#permalink]  27 Feb 2008, 20:41
1
KUDOS
sonibubu wrote:
A pool has two inlet pipes. The first inlet can fill the pool in 6 hours, the other can fill it in 4 hours. If the first pipe is open for 2 hours and then the second is open. How long will take for the pool to be filled after the second pipe is open?

1. After 2 hours working, first inlet filled = 2*1/6 = 1/3 the pool

2. When 2 inlets opened together, they must filled the remaining pool = 2/3 job

3. 1/6 + 1/4 = 2/(3*X) or X = 1.6h
_________________
Intern
Joined: 20 Feb 2008
Posts: 30
Followers: 0

Kudos [?]: 8 [1] , given: 0

Re: Rate problem [#permalink]  27 Feb 2008, 20:57
1
KUDOS
Please someone help me out by providing fully explained answer of this question.
CEO
Joined: 29 Mar 2007
Posts: 2591
Followers: 16

Kudos [?]: 233 [0], given: 0

Re: Rate problem [#permalink]  28 Feb 2008, 06:22
sonibubu wrote:
A pool has two inlet pipes. The first inlet can fill the pool in 6 hours, the other can fill it in 4 hours. If the first pipe is open for 2 hours and then the second is open. How long will take for the pool to be filled after the second pipe is open?

First pump runs for 2 hours. its rate is 1pool/6hours. Thus 2(1/6)= 1/3

1-1/3 = 2/3 of the pool remaining.

thus now just add the rates. 1/6+1/4 --> 5/12

(2/3)/(5/12) --> 8/5 or 1hr and 36 minutes.
Manager
Joined: 27 Jun 2007
Posts: 200
Followers: 3

Kudos [?]: 18 [0], given: 0

Re: Rate problem [#permalink]  28 Feb 2008, 06:43
sonibubu wrote:
A pool has two inlet pipes. The first inlet can fill the pool in 6 hours, the other can fill it in 4 hours. If the first pipe is open for 2 hours and then the second is open. How long will take for the pool to be filled after the second pipe is open?

1) First pipe open for 2 hours, thus 2 hours / 6 hours = 1/3 of the pool is filled.

Whole pool = 3/3 - 1/3 already filled = 2/3 left to be filled.

2. Second pipe is opened. Two pipes working together = 1/6 + 1/4. Common denominator = 4/24 + 6/24 = 10/24.

Factoring down 10/24, result is 5/12. This is now the rate of the two pipes working together.

To complete, take amount of pool left to be filled (2/3) divided by the rate (5/12).

(2/3) / (5/12) translates into (2/3) x (12/5) = 24/15, or 8/5.

Question asks how long it take to fill the rest of the pool after the second pipe is opened.

Answer is 1 3/5, or 1.6 hours.
Director
Joined: 20 Aug 2007
Posts: 852
Location: Chicago
Schools: Chicago Booth 2011
Followers: 11

Kudos [?]: 87 [0], given: 1

Re: Rate problem [#permalink]  29 Feb 2008, 06:32
Nice job. 1.6 hrs is correct.
Re: Rate problem   [#permalink] 29 Feb 2008, 06:32
Similar topics Replies Last post
Similar
Topics:
2 One inlet pipe fills an empty tank in 5 hours. A second inle 5 10 Feb 2014, 23:51
8 A tank has both an inlet pipe and an outlet pipe. Working 6 20 Jan 2014, 07:24
26 With both inlets open, a water tank will be filled with wate 4 31 Oct 2011, 01:07
12 A tank of volume 432 cubic feet has one inlet pipe and 2 out 15 02 Dec 2009, 00:14
1 A pond has an inlet to fill it up and an outlet to drain it. 2 27 Feb 2008, 18:15
Display posts from previous: Sort by