Ask Questions, Discuss Approaches & No Clutter
flamingo
0

Working together at their constant rates, A and B can fill an empty tank

Open 1 Answers 566 Views
GMAT Timer00:00
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 liter / min
(2) The tanks capacity is 1200 liter.
Official Answer

1 Answer

BGPC_Eliza
1
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=25 liter/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 unknowns.  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.
answered Oct 14, 2014 by Associate (125 points)
Student Speaks

Jyotsna Mehta

Indian School of Business, Co'18

I am very thankful to Gmatxchange and would definitely recommend Gmatxchange mentors to all those students applying for MBA admissions

Your Tentative GMAT Score
Estimate your GMAT score.
700
The scorer helps you to determine your current level within a few questions you solve.Read More
Please log in or register to use the Scoring Feature
Confused about your profile & colleges, Get FREE profile evaluation today from over 10 consultants.
Follow us and get quick prep updates on Facebook
...