Answer:
Given:
-> Area of the wall: 500sq. feet
-> 1 gallon of paint covers 160sq. feet of area
-> By unitary method:
-> 1 ft. square of wall requires 1/160 gallon of paint
Thus,
-> 500 ft. square of wall will require = 500 x 1/160 gallons of paint
= 3.0125 gallons
Hope it helps :)
Though my answer may be wrong :(
Have a great day!