Question

A plumbing company charges $ 42.50 plus x dollars per hour to make house calls. What would be the cost of a 90 minutes house call?
(a) 90(42.50 + x)
(b) 1.5(42.50 + x)
(c) 1.5(42.50x)
(d) 42.50 + 90x
(e) 42.50 + 1.5x

Answer 1

Hint: First of all, we will get the fixed cost and the variable cost of the house call from the given information. Then, we have to convert the given 90 minutes into hours and multiply this value with the variable cost of house call per hour. To find the final cost, we will add the fixed cost to the product of time and variable cost.

Complete step-by-step answer:
From the given information, the plumbing company charges 42.50 dollars , irrespective of the time of house call. Therefore, the fixed cost of the house call is 42.50 dollars.
The company also charges x dollars per hour to make the house call. Therefore, x is the variable cost.
Now, it is asked to find the cost of a 90 minutes house call. Each hour has 60 minutes; therefore, the number of hours will be $\dfrac{90}{60}=1.5$hours.
So, the final cost will be
(fixed cost + product of variable cost per hour and time in hours)
(42.50 + 1.5x)
Therefore, option (e) is the correct option.

Note: This is a relatively easy question which can be solved verbally if the concepts of fixed cost and variable cost are well known to the student. Conversion of units play an important part in these types of questions and students are advised to be vigilant of the units. Standard unit conversions should be known to the student.