An oil tank has a capacity of 45 gallons. At the
beginning of October it is 80% full. At the end
of October it is 1/3 full. How many gallons of
oil were used in October?

(A)21
(B)25
(C)41
(D)27
(E)30

Question

An oil tank has a capacity of 45 gallons. At the
beginning of October it is 80% full. At the end
of October it is 1/3 full. How many gallons of
oil were used in October?

(A)21
(B)25
(C)41
(D)27
(E)30

anonymous · Answer

To figure this out it would probably be easiest to start by changing the 80% into fraction form giving you 4/5. 
To find out how many gallons were in the tank at the beginning of october you would multiply 45 by the fraction we just got.
To find out how many gallons were in the tank at the end of october you would multiply the 45 capacity by 1/3 because there was 1/3 of a tank left in the end. 
To find how many gallons were used you would take the starting number of gallons minus the ending number of gallons.