The volume of the barrel is 540 liters. 85% of this barrel is filled with water. How many liters of water are in the barrel?

The unknown quantity of liters of water, which is 85% of 540 liters, is denoted by the letter X.

In proportion, we need to contrast 540 liters of water, as 100% of the total volume of the barrel, and an unknown amount of liters of water X, as 85% of the total volume of the barrel.

From the following proportion, we determine the unknown number of liters of water:

540 liters – make up 100% of the barrel volume;

X liters of water – make up 85% of the volume of the barrel;

X = 540 liters * 85% / 100% = 459 liters.

Answer: there are 459 liters of water in a barrel.