Question

A room with length 20 feet, width 16 feet, and height 12 feet is to be painted using white paint. One gallon of paint covers 100 sq ft of the wall. How many gallons of paint will be required to paint the walls and ceiling of the room on the inside?

• A. 64 gal
  
• B. 38.4 gal
  
• C. 15.04 gal
  
• D. 11.84 gal
  

Answer 1

The correct option is D 11.84 gal



Let’s open the net of a room that has 3 different pairs of rectangles.
Front + back wall:
Length = 20 ft
Height = 12 ft
Area of the first pair of opposite walls $=2\times$ area of one rectangle $=2\times l\times b$
$=2\times 20\times 12$
$=$ 480 sq ft
Side walls:
Length $=$ 16 ft
Height $=$ 12 ft
Area of the second pair of opposite walls $=2\times$ area of one rectangle $=2\times l\times b$
$=2\times 16\times 12$
$=$ 384 sq ft

Ceiling:
Length $=$ 20 ft
Width $=$ 16 ft
Area of the ceiling = area of one rectangle
$=l\times b$
$=20\times 16$
$=$ 320 sq ft
Total area to be painted $=480+384+320$
$=$ 1184 sq ft
Quantity of paint required for an area of 100 sq ft $=$ 1 gal
Quantity of paint required for an area of 1184 sq ft $=$ total area to be painted $÷$ area painted by one gallon
$=1184÷100=11.84$ gal