mgmat ds

[thephoenix]

If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water?

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.

(2) Pool X has a capacity of 14,000 gallons.
need to know short cut way
and algebraic way bth

[Rahul@gurome]

(1) Pool X is already filled to 2/7 capacity. When all the water from Pool Y is transferred to pool X, pool X gets filled to 6/7 capacity. This implies pools X and Y together contain 6/7 water to fill X.
Therefore, each pool contains 3/7 capacity water.
Pool Y has 4/7 water, so (4/7 - 3/7) = 1/7 water from pool Y needs to be transferred to pool X.
Therefore, required % of water = 1/7 * 100 = 100/7%
So, (1) is SUFFICIENT to answer the question.

(2) This statement gives no info on pool Y. So, (2) Is NOT SUFFICIENT.

[spoiler]The correct answer is (A).[/spoiler]

[kvcpk]

If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water?

YW>XW
XW = 2X/7

After k units is moved from Y to X,
YW-k is in Y
XW+k is in X

Then percentage is k/YW *100

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.

XW+YW=6X/7
2X/7 + YW = 6X/7
YW = 4X/7
So X/7 needs to be moved form YW so that both YW and XW are same.

Percentage is (X/7)/4X/7 * 100 = 25%
So SUFFICIENT.

(2) Pool X has a capacity of 14,000 gallons.
X = 14000
so XW = 2X/7 = 4000
We have no information about YW
So INSUFFICIENT.

Pick A.

[kvcpk]

Therefore, required % of water = 1/7 * 100 = 100/7%
So, (1) is SUFFICIENT to answer the question.

We need percentage of water with respect to pool Y. hence it should be (1/7)/(4/7) * 100 = 25%
Isnt it so?

[Rahul@gurome]

Therefore, required % of water = 1/7 * 100 = 100/7%
So, (1) is SUFFICIENT to answer the question.

We need percentage of water with respect to pool Y. hence it should be (1/7)/(4/7) * 100 = 25%
Isnt it so?

U r right, missed it. Thanks.

[gmatinamonth]

Option 2 is useless, so eliminate B and D
X is filled to 2/7 capacity and after adding Y becomes 6/7, so we know how much Y contains and the amt that needs to be added, so the question can be solved, so answer is A.

You dont need to get the actual answer.

Y contains 4/7, 1/7 needs to be transferred, so its 25 %