Beat The GMAT

money9111 · Sun Jan 31, 2010 10:55 pm

After 4,000 gallons of water were added to a large water tank that was already filled to 3/4 of its capacity, the tank was then at 4/5 of its capacity. How many gallons of water does the tank hold when filled to capacity?

a. 5,000
b. 6,200
c. 20,000
d. 40,000
e. 80,000

How do you set this up initially?

Sidenote - if someone can tell me how to hide the answer so people can highlight over it... i'll do that when I post questions. I just don't know how to do that right now :-/

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ajith · Sun Jan 31, 2010 11:07 pm

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money9111 · Sun Jan 31, 2010 11:08 pm

hhhm like this? testing testing 123

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papgust · Sun Jan 31, 2010 11:09 pm

Let 'x' be the total capacity of a tank.

Already filled tank is (3/4 * x)

After 4000 gallons were poured in, filled tank is (4/5 * x)

So, (4x/5 - 3x/4) = 4000

16x - 15x = 4000 * 20

x = 80,000.

Note: You can highlight the OA and click button 'Spoiler' to hide the answer.