Question

Tom wants to paint his study room. One of the walls of the room measures $12\text{feet}\times 11\text{feet}$, and the base measures $11\text{feet}\times 9\text{feet}$. Find the cost of painting all the four walls if the cost of painting is $\$3$ per square feet.

• A. $\$1440$
• B. $\$1420$
• C. $\$1240$
• D. $\$1280$

Answer 1

The correct option is A $\$1440$

Let's draw a rectangular prism with appropriate dimensions.

Given,
Length of the rectangular prism ($l$) = 11 ft
Width of the rectangular prism ($w$) = 9 ft
Height of the rectangular prism ($h$) = 12 ft
We know that the lateral surface area of the rectangular prism $=2(l+w)\times h$
$=2(11+9)\times 12=2\times 20\times 12=480\text{sq ft}$
Given, the cost of painting is $\$3$ per sq ft.
Hence, the total cost of painting is $3\times 480=\$1440$.