Bunuel wrote:

A tank that was 40% full of oil was emptied into a 20-gallon bucket. If the oil fills 35% of the bucket’s volume, then what is the total capacity of the tank, in gallons?

(A) 8.75

(B) 15

(C) 16

(D) 17.5

(E) 19

Find the # of gallons of oil from the bucket

Reverse the process: find the capacity of the tank from the number of gallons of oil

1) # of gallons of oil?

20-gallon total capacity becomes 35% full when oil is poured in

35% of 20 = # of gallons of oil

\((20 * .35) = 7\) gallons of oil

2) Capacity of TANK?

7 gallons of oil equaled 40 percent of a full tank's capacity, T

\(7 = (.40*T)\)

\(T =\frac{7}{.4}=\frac{70}{4}=17.5\)

Answer D

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