It is currently 19 Jan 2018, 21:24

### 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

# The radius of a cylindrical water tank is reduced by 50%. Ho

Author Message
TAGS:

### Hide Tags

Intern
Status: gmat fresher
Joined: 07 Jun 2012
Posts: 25

Kudos [?]: 238 [0], given: 12

GPA: 3.87
The radius of a cylindrical water tank is reduced by 50%. Ho [#permalink]

### Show Tags

19 Dec 2013, 11:05
2
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

71% (01:23) correct 29% (01:23) wrong based on 101 sessions

### HideShow timer Statistics

The radius of a cylindrical water tank is reduced by 50%. However, the speed by which water is filled into the tank is also decreased by 50%. How much more or less time will it take to fill the tank now?

(A) 50% less time
(B) 50% more time
(C) 75% less time
(D) 75% more time
(E) 100% more time
[Reveal] Spoiler: OA

Last edited by Bunuel on 19 Dec 2013, 11:41, edited 1 time in total.
RENAMED THE TOPIC.

Kudos [?]: 238 [0], given: 12

Manager
Joined: 19 Apr 2013
Posts: 77

Kudos [?]: 91 [1], given: 9

Concentration: Entrepreneurship, Finance
GMAT Date: 06-05-2015
GPA: 3.88
WE: Programming (Computer Software)
Re: The radius of a cylindrical water tank is reduced by 50%. Ho [#permalink]

### Show Tags

19 Dec 2013, 21:51
1
KUDOS
sdpp143 wrote:
The radius of a cylindrical water tank is reduced by 50%. However, the speed by which water is filled into the tank is also decreased by 50%. How much more or less time will it take to fill the tank now?

(A) 50% less time
(B) 50% more time
(C) 75% less time
(D) 75% more time
(E) 100% more time

It can be solved in very simpler way.

(VC)Volume of the cylinderical vessal is directly proportional to R^2.

So if radius is 50% less volume will be 1/4th of the original volume.(VC/4)

Now if with velocity V tank can be filled in T1 time of volume VC

So now Velocity is 50% less i..e V/2

So time taken to fill the capacity VC/4 by V/2 velocity is T2.

VT1 = VC

V/2*T2 = VC/4

So T1/T2 = 1/2

So Tank will be filled in less time. that is 50 % less.

Thanks,
AB

+1 Kudos if you like and understand.

_________________

Thanks,
AB

+1 Kudos if you like and understand.

Kudos [?]: 91 [1], given: 9

Manager
Joined: 15 Aug 2013
Posts: 59

Kudos [?]: 29 [0], given: 7

Re: The radius of a cylindrical water tank is reduced by 50%. Ho [#permalink]

### Show Tags

19 Dec 2013, 23:44
Since radius is reduced by 50%, the new volume becomes 1/4 of the original volume. Also the speed is reduced by 50% i.e. new speed is 1/2 of the original speed.
If the voume would have been same, then with half of the speed the time taken would be double. ALso the volume is reduced by 1/4 of original. Hence time taken effectively will be 2/4 i.e. 1/2 of the original. Therefore 50% less time than normal.

Ans- (A)

Kudos [?]: 29 [0], given: 7

VP
Joined: 22 May 2016
Posts: 1252

Kudos [?]: 463 [2], given: 683

The radius of a cylindrical water tank is reduced by 50%. Ho [#permalink]

### Show Tags

04 Dec 2017, 10:51
2
KUDOS
sdpp143 wrote:
The radius of a cylindrical water tank is reduced by 50%. However, the speed by which water is filled into the tank is also decreased by 50%. How much more or less time will it take to fill the tank now?

(A) 50% less time
(B) 50% more time
(C) 75% less time
(D) 75% more time
(E) 100% more time

Pick smart numbers, and this question can be answered pretty quickly.

Original cylinder
Let r = 4 ft
Let h = 2 ft
Find volume, then pick a rate.

Volume of original cylinder, in cubic feet:
$$\pi r^2h=(\pi*16*2)= 32\pi$$

Choose a smart fill rate for $$32\pi$$.
Let fill rate, in cu. feet per hr = $$\frac{16\pi}{1hr}$$

Time to fill original cylinder:
$$\frac{Volume}{rate}= Time$$

$$\frac{32\pi}{(\frac{16\pi}{1})}= 32\pi* \frac{1}{16\pi}= 2$$ hours

New cylinder

r = .50(4) = 2 feet
h = 2 feet
Volume of new cylinder, in cu. feet:
$$\pi r^2h=(\pi*4*2)= 8\pi$$

Fill rate decreases by 50 percent:
$$\frac{16\pi}{1hr}*(\frac{1}{2}) = \frac{8\pi}{1hr}$$

Time to fill new cylinder:
$$\frac{Volume}{rate}=Time$$

$$\frac{8\pi}{(\frac{8\pi}{1})}= 8\pi* \frac{1}{8\pi}= 1$$ hour

Percent change in time to fill
How much more or less time will it take to fill the tank now?

Percent change:
$$\frac{New-Old}{Old}*100$$

$$\frac{1-2}{2}*100=-\frac{1}{2}*100=-.50*100=-50$$
%

_________________

At the still point, there the dance is. -- T.S. Eliot
Formerly genxer123

Kudos [?]: 463 [2], given: 683

Manager
Status: Enjoying the Journey
Affiliations: ND
Joined: 26 Sep 2017
Posts: 89

Kudos [?]: 39 [1], given: 533

Schools: Rotman '21
WE: Marketing (Consulting)
Re: The radius of a cylindrical water tank is reduced by 50%. Ho [#permalink]

### Show Tags

25 Dec 2017, 01:22
1
KUDOS
Volume = $$πr^2h$$
New Volume= $$π(r/2)^2h$$ = $$1/4 (πr^2h)$$

Time =V/R
New Time= 1/4V ÷ R/2= 1/2 (V/R) = 50% less time

_________________

"Giving kudos" is a decent way to say "Thanks" and motivate contributors. Please use them, it won't cost you anything

High achievement always takes place in the framework of high expectation Charles Kettering
If we chase perfection we can catch excellence Vince Lombardi

GMAT Club Live: 5 Principles for Fast Math: https://gmatclub.com/forum/gmat-club-live-5-principles-for-fast-math-251028.html#p1940045
The Best SC strategies - Amazing 4 videos by Veritas: https://gmatclub.com/forum/the-best-sc-strategies-amazing-4-videos-by-veritas-250377.html#p1934575

Kudos [?]: 39 [1], given: 533

Re: The radius of a cylindrical water tank is reduced by 50%. Ho   [#permalink] 25 Dec 2017, 01:22
Display posts from previous: Sort by