Question

What is the cost in dollars to steam clean a room W yards wide and L yards long, if the steam cleaner charges $10\;cents$ per square foot?
(A) $0.9WL$
(B) $0.3WL$
(C) $0.1WL$
(D) $9WL$
(E) $3WL$

Answer 1

Hint: In order to solve this question, here we will first convert the units of length and breadth of the room from yards to feet and then by using the general relation between the value of money from cents to dollars we will calculate the actual cost of steam clean for the area of the room in dollars.

Complete step-by-step answer:
According to the question, we have given that the
length of the room is L yards
converting this unit in to feet as we know that $1yard = 3feet$ so
$l = 3L{\kern 1pt} feet$ where l is length of room
similarly we have given that breadth of the room is W yards so again, we have
$b = 3W{\kern 1pt} feet$ where b is Breadth of the room.
So, Total area A of the room simply as
$A = l \times b$ on putting the values we have,
$A = 9WL{\kern 1pt} {\kern 1pt} fee{t^2}$
Now, it’s given to us that per square feet the cost is $10cents$ and we also know that,
$10cents = \dfrac{1}{{10}}dollars$ so total cost is calculated as
$\operatorname{Cos} t = A \times \dfrac{1}{{10}}{\kern 1pt} dollar$
$\operatorname{Cos} t = 9WL \times \dfrac{1}{{10}}{\kern 1pt} dollar$
so, cost in dollars is $0.9WL$
So, the correct answer is “Option A”.

Note: It should be remembered that, while solving such questions, keep in mind these basic units of conversions as $1yard = 3feet$ and the conversions of value of money as $1cents = \dfrac{1}{{100}}dollars$ and area of any rectangular surface is simple the product of its length and breadth of the rectangular surface.