A13.5 gallon gasoline tank is 2/3 full. how many gallons will it take to fill the tank?

Let's look at all the information given to us.

- The tank can hold 13.5 gallons

- It is 2/3 full

And now the question it's asking.

- How many gallons to fill it?

Essentially, it's asking how to make the tank 100% full when it's already 2/3 of the way full.

To solve:

What fraction of the tank needs to be filled up?

100% is also equal to 3/3.

The difference between 2/3 and 100% therefore, can be rewritten as the difference between 3/3 and 2/3. Then it's clearer that the amount the tank needs to be filled is 1/3 of it's maximum capacity.

The maximum capacity is 13.5 gallons.

What's 1/3 of 13.5? To get that, multiply 1/3 by 13.5, to get 4.5.

Therefore, 4.5 is 1/3 of 13.5, and is therefore the amount of gasoline the tank needs to be filled up.

Your answer is 4.5 gallons.