A rainstorm increased the amount of water stored in State J reservoirs from 5 billion gallons to 7.5 billion gallons. If the storm increased the amount of water in the reservoirs to 55 percent of total capacity, approximately how many billion gallons of water were the reservoirs short of total capacity prior to the storm?
Choose the correct option:  A) 6.9  B) 1.4  C) 2.5  D) 3.0  E) 4.4

Rationale: after the reservoir is filled to 7.5 gallons the amount of water is at 55 % - which means that 45 % of the reservoir is empty . to figure out what that 45 % is approximate : 7.5 gallons / 55 percent = x gallons / 45 percent , therefore , x = 6.136 gallons , answer choices e , b , c , d are below 6.136 . we know that the reservoir must be short more than 6.136 gallons , therefore , the only possible choice is a .
Answer: A