How high must a 40 gallon tank be if the base is a square 3 feet 9 inches on a side

so if the base is a square, which is 3'9" on a side, that means the tank is just a tall square, namely a rectangular prism.

since there are 12 inches in 1 foot, then 3 feet is 36 inches, and 3'9" is then 36" + 9" or 45 inches, so the base is a 45"x45" square.

now, let's covert the gallons to inches as well, namely in³, keeping in mind a (US) gallon has 231 in³, then 40 gallons will be 40*231 or 9240 in³.

use an equation of ratios to determine the amount of gas needed to fill the tank.

    0.2             0.8

  =    

288.75             x

                                                              231 gal

so, 0.2x = (0.8)(288.75 gal), and x = = 1155 gal.

                                                                0.2

it would take 1155 gal. to fill the tank.

the cost would be

1155 gal         $3

* = $3465   (answer)

      1           1 gal

hope this you