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

 It is currently 22 Feb 2019, 04:25

### 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 February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT RC Webinar

February 23, 2019

February 23, 2019

07:00 AM PST

09:00 AM PST

Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
• ### FREE Quant Workshop by e-GMAT!

February 24, 2019

February 24, 2019

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# In what time would a cistern be filled by three pipes whose diameters

Author Message
TAGS:

### Hide Tags

VP
Joined: 05 Mar 2015
Posts: 1001
In what time would a cistern be filled by three pipes whose diameters  [#permalink]

### Show Tags

21 Jan 2017, 09:23
2
11
00:00

Difficulty:

75% (hard)

Question Stats:

63% (03:01) correct 38% (03:28) wrong based on 79 sessions

### HideShow timer Statistics

In what time would a cistern be filled by three pipes whose diameters are 1cm , 4/3 cm , 2 cm,running together, when the largest alone will fill it in 61 minutes, the amount of water flowing in by each pipe being proportional to square of its diameter ??

A. 18 minutes
B. 20 minutes
C. 40 minutes
D. 36 minutes
E. 72 minutes.

Source :- Quicker Maths
Senior Manager
Joined: 13 Oct 2016
Posts: 367
GPA: 3.98
Re: In what time would a cistern be filled by three pipes whose diameters  [#permalink]

### Show Tags

21 Jan 2017, 12:33
rohit8865 wrote:
In what time would a cistern be filled by three pipes whose diameters are 1cm , 4/3 cm , 2 cm,running together, when the largest alone will fill it in 61 minutes, the amount of water flowing in by each pipe being proportional to square of its diameter ??

A. 18 minutes
B. 20 minutes
C. 40 minutes
D. 36 minutes
E. 72 minutes.

Source :- Quicker Maths

This one gave a real headache.

Rate of 3 pipes working together:

$$\frac{1}{N}$$, $$N = x + 4x + \frac{16x}{9} = \frac{61x}{9}$$

$$\frac{1}{N} = \frac{9}{61x}$$

Rate of the biggest pipe = $$\frac{1}{4x}$$

$$\frac{1}{4x} ---> 61 (min)$$

$$\frac{9}{61x} ----> y (min)$$

$$\frac{y}{4x} = \frac{9*61}{61x}$$

$$\frac{y}{4x} = \frac{9}{x}$$

$$y*x = 36*x$$

$$y = 36 min$$

VP
Joined: 07 Dec 2014
Posts: 1154
In what time would a cistern be filled by three pipes whose diameters  [#permalink]

### Show Tags

21 Jan 2017, 13:03
rohit8865 wrote:
In what time would a cistern be filled by three pipes whose diameters are 1cm , 4/3 cm , 2 cm,running together, when the largest alone will fill it in 61 minutes, the amount of water flowing in by each pipe being proportional to square of its diameter ??

A. 18 minutes
B. 20 minutes
C. 40 minutes
D. 36 minutes
E. 72 minutes.

Source :- Quicker Maths

rate of largest pipe=1/61
rate of smallest pipe=(1/2)^2*1/61=1/(4*61)
rate of middle pipe=(2/3)^2*1/61=4/(9*61)
let t=time for all three pipes to fill cistern
1+1/4+4/9=61*1/t
61/36=61/t
t=36 minutes
D
Non-Human User
Joined: 09 Sep 2013
Posts: 9887
Re: In what time would a cistern be filled by three pipes whose diameters  [#permalink]

### Show Tags

08 Oct 2018, 04:17
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: In what time would a cistern be filled by three pipes whose diameters   [#permalink] 08 Oct 2018, 04:17
Display posts from previous: Sort by