Image used in answering the question is attached below.
Answer: 21.97gallons
Step-by-step explanation:
Calculating the total area to be painted :
The exterior four walls :
The exterior walls have rectangular front, back and two sides.
Area of rectangular front and back :
Length(L) = 32ft
Width(W) = 20ft
Area of rectangle = L × W
32 × 20 = 640ft^2
Front and back = 640ft^2 × 2 = 1280ft^2
Area of rectangular sides :
Length = 84
Width = 20
2 × (84 × 20) = 3360ft^2
Area of triangular front and back :
Area of triangle = (0.5) × base × height
Base = 38ft, height = 12ft
(0.5) × 38 × 12 = 228ft^2
Two triangles = 2 × 228 = 456ft^2
Total area to be painted :
(456 + 3360 + 1280)ft^2 = 5096ft^2
Gallons required = total area to be painted / area covered by one gallon
5096ft^2/232ft^2 = 21.965gallons