The time it takes to fill a tank varies directly with the volume of the tank. if it takes 1 hour to fill a 400 gallone tank, how long will it take to fill a 600 gallon tank.

The direct variation of the time it takes to fill the tank with the volume of the tank may be presented by the following equation,

V = kt

where V is volume, t is time and k is the constant of direct variation.

To solve for k, substitute the known data in the equation above,

400 gal = k (1 hour); k = 400 gal / h

For the second condition,

600 gal = (400 gal/h) t; t = 1.5 hours

Therefore, it will take 1.5 hours to fill a 600-L tank.