If 5 gallons of gasoline are added to a tank that is already filled to 3/4 of its capacity, the tank is then filled to 9/10 of its capacity. How many gallons does the tank hold? Options
A) 20 B) 30 C) 36 D) 40 E) 60

Rationale: let the capacity of the tank = c ( 3 / 4 ) c + 5 = ( 9 / 10 ) c = > ( 9 / 10 ) c - ( 3 / 4 ) c = 5 = > ( 3 / 20 ) c = 5 = > c = ( 5 * 20 ) / 3 = 33.33 number of gallons of gasoline that the tank currently holds = 3 / 4 * c + 5 = 24.99 + 5 = 29.99 = 30 answer b
Answer: B