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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: Data sufficiency work rate problem [#permalink]

Show Tags

15 Jul 2010, 17:18

1

This post received KUDOS

2

This post was BOOKMARKED

ksharma12 wrote:

15. working together at their constant rates , A and B can fill an empty tank to capacity in1/2 hr.what is the constant rate of pump B? 1) A's constant rate is 25LTS / min 2) the tanks capacity is 1200 lts.

Can someone solve this beyond just showing what is sufficient?

I know the answer is A but I need to know how to solve to fully grasp the concept of only needing the first statement.

Thank you

Question: If A and B can fill 2 tanks in 1 hour together, then how many tanks can B fill up in 1 hour alone?

I'm setting this up as ratios of "x tanks per 1 hour" : \(\frac{a}{1hr}+\frac{b}{1hr}= \frac{2}{1hr}\)

1) This does NOT give you "a" because you need to know the size of the tanks. As we stated above, the ratios above show how many TANKS per hour each can fill, not how many gallons or liters. NOT sufficient

2) This gives you the tank's capacity, which is valuable in combination with 1). However, just knowing the tank's volume isn't useful since we don't know the flow rate of A. NOT sufficient

Now that we have both the flow rate and the volume of the tank, we can easily find the value of "a" in the above equation. Both statements together are sufficient.

Are you sure the answer is A? I definitely think it is C. Where is this question from?

15. working together at their constant rates , A and B can fill an empty tank to capacity in1/2 hr.what is the constant rate of pump B? 1) A's constant rate is 25LTS / min 2) the tanks capacity is 1200 lts.

Can someone solve this beyond just showing what is sufficient?

I know the answer is A but I need to know how to solve to fully grasp the concept of only needing the first statement.

Thank you

Answer to this question is C not A.

\(rate*time=job\).

We are told that \((A+B)*30=C\), where \(A\) is the rate of pump A in lts/min, \(B\) is the rate of pump B in lts/min and C is the capacity of the tank in liters.

Question: \(B=?\)

(1) \(A=25\) --> \((25+B)*30=C\) --> clearly insufficient (two unknowns), if \(C=1200\), then \(B=15\) but of \(C=1500\), then \(B=25\).

(2) \(C=1200\). \((A+B)*30=1200\) --> \(A+B=40\). Also insufficient.

(1)+(2) \(A=25\) and \(A+B=40\) --> \(B=15\). Sufficient.

Re: working together at their constant rates , A and B can fill [#permalink]

Show Tags

27 Dec 2012, 03:07

2

This post received KUDOS

1

This post was BOOKMARKED

smartmanav wrote:

Can't we do this question using unitary method ?

Hi Smartmanav,

I guess this cannot be done by Unitary method as we are given the Constant rate of A i.e 25L/min. Now does it tell you the time A will take alone to fill the tank. No, because we do not the volume/size of the tank.

That is why method suggested by Bunuel of Rate*Time =Work

Thanks Mridul
_________________

“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”

Re: Working together at their constant rates, A and B can fill [#permalink]

Show Tags

29 Aug 2013, 18:13

1

This post received KUDOS

1

This post was BOOKMARKED

The standard formula for solving this problem is AB/A+B=1/2 hrs we need A to get to B, where A is the time taken by Pipe A to fill ENTIRE tank alone from options the time taken by Pipe A to fill ENTIRE tank alone=1200/25=48 minutes substitute in equation above to get value of B. SIMPLE!

Re: Working together at their constant rates, A and B can fill [#permalink]

Show Tags

14 Oct 2014, 03:22

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: Working together at their constant rates, A and B can fill [#permalink]

Show Tags

14 Oct 2014, 08:39

1

This post received KUDOS

So let's put this into an equation. We know that (Arate+Brate)30min=T, if T= the tank's capacity.

(1) now we know that Arate=25lirer/min, so we can plug that into the equation and we get (25lit/min+Brate)30min=T

This is not sufficient, because there are still too many unkowns. For example, it T=900 liters then Brate would equal 5 liters/min. But if T=9,000 then Brate would equal 275 liters/min

(2) now we know that T= 1200 liters, plugging that into the equation we get (Arate+Brate)30min=1200 liters

This is also not sufficient, because there are a variety of different combinations of Arate and Brate that can fit this equation. For example, Arate could be 10 liters per min and Brate could be 30 liters per min OR vice versa.

Now lets try them both together by plugging (1) and (2) into the equation:

(25lit/min+Brate)30min=1200 liters

divide both sides by 30 min and we get: 25 liters/min+Brate=40liters/min

that means Brate equals 15 liters, so the answer is (C) both together are sufficient

In the actual GMAT, you would not need to go so far as to figure out exactly what B rate. That would be a waste of time. As soon as you know what you CAN solve it with both, which can be determined by the fact that there is only 1 unknown then you should select C and move on.
_________________

Re: Working together at their constant rates, A and B can fill [#permalink]

Show Tags

27 Oct 2015, 12:07

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: Working together at their constant rates, A and B can fill [#permalink]

Show Tags

01 Aug 2016, 06:59

ksharma12 wrote:

Working together at their constant rates, A and B can fill an empty tank to capacity in 1/2 hours. What is the constant rate of pump B?

(1) A's constant rate is 25 LTS / min (2) The tanks capacity is 1200 lts.

ksharma12 wrote:

Working together at their constant rates, A and B can fill an empty tank to capacity in 1/2 hours. What is the constant rate of pump B?

(1) A's constant rate is 25 LTS / min (2) The tanks capacity is 1200 lts.

Let the rate of A be a and the rate of B be b

(1) A's constant rate is 25 LTS / min (a+b)time = Volume of tank (25+b)*30 minutes = Volume of tank 750+30b = volume of tank Rate of B and the volume of tank is not known INSUFFICIENT

(2) The tanks capacity is 1200 lts. (a+b)*time = 1200 (a+b)*30 minutes = 1200 30a+30b=1200 Rate of A and rate of B is not known INSUFFICIENT

MERGE BOTH 750 + 30b= 30a+30b {since both equations are equal to 1200} 30a=750 a=750/30 = 25

Now rate of A is known. Rate of B can be easily calculated by putting value of in any equation for example 30a+30b =1200 750+30b=1200 30b=450 b= 15

SUFFICIENT

ANSWER IS C

we need both statements together

ANSWER IS C
_________________

Posting an answer without an explanation is "GOD COMPLEX". The world doesn't need any more gods. Please explain you answers properly. FINAL GOODBYE :- 17th SEPTEMBER 2016.

gmatclubot

Re: Working together at their constant rates, A and B can fill
[#permalink]
01 Aug 2016, 06:59

After days of waiting, sharing the tension with other applicants in forums, coming up with different theories about invites patterns, and, overall, refreshing my inbox every five minutes to...

I was totally freaking out. Apparently, most of the HBS invites were already sent and I didn’t get one. However, there are still some to come out on...

In early 2012, when I was working as a biomedical researcher at the National Institutes of Health , I decided that I wanted to get an MBA and make the...