Bunuel wrote:
As shown in the figure above, a cylindrical oil tank is i full. If 3 more gallons are added, the tank will be half full. What is the capacity, in gallons, of the tank?
(A) 15
(B) 16
(C) 17
(D) 18
(E) 19
Attachment:
2018-02-08_1636.png
We can let n = the total capacity and create the equation:
n/3 + 3 = n/2
Multiplying by 6 we have:
2n + 18 = 3n
18 = n
Alternate Solution:
The amount of oil in the tank increases from 1/3 to 1/2, which is 1/2 - 1/3 = 3/6 - 2/6 = 1/6 of the tank, and this is equal to 3 gallons. We see that if 3 gallons is 1/6 of the tank’s capacity, then 3 x 6 = 18 gallons is the tank’s total capacity.
Answer: D
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92% (00:55) correct 
