[email protected] wrote:Two water tanks, X and Y, were drained simultaneously. If X contained 30 more gallons of water than Y, and both tanks became empty at the same time, how long did it take the tanks to empty?
(1) For every gallon drained from tank Y, 2 gallons were drained from tank X.
(2) Tank Y was drained at a constant rate of 20 gallons per hour
Since X contains 30 more gallons than Y, we get:
X=Y+30.
Statement 1: For every gallon drained from tank Y, 2 gallons were drained from tank X.
Since tank X is drained TWICE AS FAST as tank Y, and both tanks become empty AT THE SAME TIME, tank X must contain TWICE AS MANY GALLONS as tank Y.
Thus, X=2Y.
Since X=Y+30 and X=2Y, we get:
Y+30 = 2Y
30 = Y.
No way to determine how much time is required to empty the two tanks.
INSUFFICIENT.
Statement 2: Tank Y was drained at a constant rate of 20 gallons per hour.
If Y=20 gallons, then the time required to empty each tank = w/r = 20/20 = 1 hour.
If Y=40 gallons, then the time required to empty each tank = w/r = 40/20 = 2 hours.
Since the time can be different values, INSUFFICIENT.
Statements combined:
Statement 1: Y = 30 gallons.
Statement 2: Rate = 20 gallons per hour.
Thus, the time required to empty each tank = w/r = 30/20 = 1.5 hours.
SUFFICIENT.
The correct answer is
C.
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