# Fraction problem: A car tank is 3/5 full. After using 6 liters, it is only 9/20 full.

#### Cristeljoy

##### New member
A car tank is 3/5 full. After using 6 liters, it is only 9/20 full. How many liters does it hold when full?

#### mmm4444bot

##### Super Moderator
Staff member
Let x = liters in a full tank.

To say the tank is 3/5ths fulls means there are (3/5)x liters of fuel.

To say the tank is 9/20ths full means there are (9/20)x liters.

Can you use these expressions, to form an equation, based on the given information that using 6 liters of the first amount leaves the second amount? :cool:

#### stapel

##### Super Moderator
Staff member
A car tank is 3/5 full. After using 6 liters, it is only 9/20 full. How many liters does it hold when full?
The six liters used 3/5 - 9/20 = 12/20 - 9/20 = 3/20 of a tank. Since 6 liters is 3/20 of a tank, then 2 liters is 1/20 of a tank. So how much is the whole tank? :wink: