naveenhv wrote:
When n liters of fuel was added to a tank that was already 1/3 full, the tank was filled to 7/9 of its capacity. In terms of n, what is the capacity of the tank, in liters?
A. 10/9 n
B. 4/3 n
C. 3/2 n
D. 9/4 n
E. 7/3n
When you see
variables in the answer choices, use
smart numbers.
Suppose that the capacity of the tank is 27 liters. (I chose 27 because it's divisible by the other numbers in the problem). In that case, the tank already contained 9 liters, and when we added a certain amount, it was filled to 7/9(27), or 21 liters. That means n = 21-9 = 12.
So, n = 12, and the capacity is 27. Try plugging 12 into the answer choices, and see whether you end up with 27.
(A) 10/9(12) isn't an integer!
(B) 4/3(12) = 16 - too small
(C) 3/2(12) = 18 - too small
(D) 9/4(12) = 27 -
perfect!(E) 7/3(12) = 28 - too big
_________________