After a storm deposits 120 billion gallons of water into the city reservoir, the reservoir is 85% full. If the original contents of the reservoir totaled 220 billion gallons, the reservoir was approximately what percentage full before the storm?  Choose the correct choice
A) 45 % B) 48 % C) 55 % D) 58 % E) 65 %

Rationale: "when the storm deposited 120 billion gallons , volume of water in the reservoir = 220 + 120 = 340 billion gallons if this is only 85 % of the capacity of the reservoir , the total capacity of the reservoir = 340 / 0.85 = 400 billion gallons therefore percentage of reservoir that was full before the storm = ( 220 / 400 ) * 100 = 55 % option c"
Answer: C