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

 It is currently 25 Apr 2019, 18:59

### 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

# M19-04

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 54544
M19-04  [#permalink]

### Show Tags

16 Sep 2014, 01:05
00:00

Difficulty:

5% (low)

Question Stats:

91% (01:04) correct 9% (01:07) wrong based on 187 sessions

### HideShow timer Statistics

Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 54544
Re M19-04  [#permalink]

### Show Tags

16 Sep 2014, 01:05
1
Official Solution:

Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

The valves could fill the whole pool in $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$ hours. Therefore they would fill a fifth of the pool in $$\frac{2}{5}*60 = 24$$ minutes.

Answer: C
_________________
Intern
Joined: 27 Jul 2017
Posts: 19
Location: Spain
Schools: IMD '20
GMAT 1: 570 Q42 V27
GPA: 2.9
Re: M19-04  [#permalink]

### Show Tags

27 Jul 2017, 04:35
Hi, i got the correct answer but it took me around 4minutes. I did it in a different way though...
Can you explain why you divide 1/1/3+1/6?? I really don´t get it.
Thanks

Bunuel wrote:
Official Solution:

Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

The valves could fill the whole pool in $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$ hours. Therefore they would fill a fifth of the pool in $$\frac{2}{5}*60 = 24$$ minutes.

Answer: C
Math Expert
Joined: 02 Sep 2009
Posts: 54544
Re: M19-04  [#permalink]

### Show Tags

27 Jul 2017, 04:54
1
juanito1985 wrote:
Hi, i got the correct answer but it took me around 4minutes. I did it in a different way though...
Can you explain why you divide 1/1/3+1/6?? I really don´t get it.
Thanks

Bunuel wrote:
Official Solution:

Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

The valves could fill the whole pool in $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$ hours. Therefore they would fill a fifth of the pool in $$\frac{2}{5}*60 = 24$$ minutes.

Answer: C

(rate)(time) = (job done)

So, (time) = (job done)/(rate).

The combined rate of the valves is $$\frac{1}{3} + \frac{1}{6}$$. Hence $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$
_________________
Intern
Joined: 27 Jul 2017
Posts: 19
Location: Spain
Schools: IMD '20
GMAT 1: 570 Q42 V27
GPA: 2.9
Re: M19-04  [#permalink]

### Show Tags

27 Jul 2017, 05:01
Bunuel wrote:
juanito1985 wrote:
Hi, i got the correct answer but it took me around 4minutes. I did it in a different way though...
Can you explain why you divide 1/1/3+1/6?? I really don´t get it.
Thanks

Bunuel wrote:
Official Solution:

Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

The valves could fill the whole pool in $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$ hours. Therefore they would fill a fifth of the pool in $$\frac{2}{5}*60 = 24$$ minutes.

Answer: C

(rate)(time) = (job done)

So, (time) = (job done)/(rate).

The combined rate of the valves is $$\frac{1}{3} + \frac{1}{6}$$. Hence $$\frac{1}{\frac{1}{3} + \frac{1}{6}} = 2$$

Got it! Very straight forward. Thank you so much!
Senior Manager
Joined: 08 Jun 2015
Posts: 426
Location: India
GMAT 1: 640 Q48 V29
GMAT 2: 700 Q48 V38
GPA: 3.33
Re: M19-04  [#permalink]

### Show Tags

27 Jul 2017, 06:16
+1 for C. Use time and rate approach to solve this question. Both can fill the tank in 2 hours. To fill 1/5 of the tank we need (2/5)*60 or 24 minutes.
_________________
" The few , the fearless "
Director
Joined: 04 Dec 2015
Posts: 750
Location: India
Concentration: Technology, Strategy
WE: Information Technology (Consulting)
M19-04  [#permalink]

### Show Tags

27 Jul 2017, 06:28
1
Bunuel wrote:
Valve 1, if open, would fill a pool in 3 hours. Valve 2, if open, would fill the pool in 6 hours. If both valves are opened simultaneously, how long will it take to fill the pool to $$\frac{1}{5}$$ of its capacity?

A. 18 minutes
B. 20 minutes
C. 24 minutes
D. 30 minutes
E. 36 minutes

Valve $$1$$ can fill pool in $$3$$ hours.
Valve $$1$$ per hour rate of work $$= \frac{1}{3}$$

Valve $$2$$ can fill pool in $$6$$ hours.
Valve $$2$$ per hour rate of work $$= \frac{1}{6}$$

$$1$$ hour rate of work of Valve $$1$$ and Valve $$2$$ working together is;

$$\frac{1}{3} + \frac{1}{6} = \frac{2 + 1}{6} = \frac{3}{6} = \frac{1}{2}$$

Both valves working together can fill the pool in $$= \frac{1}{(1/2)} = 2$$ hours $$= 120$$ minutes

Therefore both valves working together can fill the pool to $$\frac{1}{5}$$ of its capacity in $$= \frac{1}{5} * 120 = 24$$ minutes

Answer (C)...
Retired Moderator
Joined: 19 Mar 2014
Posts: 931
Location: India
Concentration: Finance, Entrepreneurship
GPA: 3.5
Re: M19-04  [#permalink]

### Show Tags

28 Jul 2017, 00:45
A - 1/3 Per Hour

B = 1/6 Per Hour

A & B together 1/3 + 1/6 = 1/2 per hour

we want to calculate the time for 1/5 of the pool

= 60 * 1/5 = 1/2 * x

x = 60 * 1/5 * 2

x = 24 minutes

hence, C
_________________
"Nothing in this world can take the place of persistence. Talent will not: nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not: the world is full of educated derelicts. Persistence and determination alone are omnipotent."

Best AWA Template: https://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html#p470475
Re: M19-04   [#permalink] 28 Jul 2017, 00:45
Display posts from previous: Sort by

# M19-04

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

Moderators: chetan2u, Bunuel

 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®.