milind1979 wrote:

When 200 gallons of oil were removed from a tank, the volume of oil left in the tank was \(\frac{3}{7}\) of the tank's capacity. What was the tank’s capacity?

(1) Before the 200 gallons were removed, the volume of oil in the tank was \(\frac{1}{2}\) of the tank's capacity.

(2) After the 200 gallons were removed, the volume of the oil left in the tank was 1,600 gallons less than the tank's capacity.

When 200 Gallons was removed - 3/7 was left of tank's capacity.

With this in order to calculate the tanks capacity, we need to know what does 200 gallons corresponds to or what is the remaining 3/7 capacity corresponds to.

(1) Before the 200 gallons were removed, the volume of oil in the tank was \(\frac{1}{2}\) of the tank's capacity.

Provides information on what 200 gallons corresponds to overall tank volume, hence sufficient.

(2) After the 200 gallons were removed, the volume of the oil left in the tank was 1,600 gallons less than the tank's capacity.

Provides information on what the 3/7th volume corresponds to, hence sufficient.

Answer is D
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