Algebra Demystified 2nd Ed

Chapter 8 linear appliCaTionS 237

If degrees Fahrenheit and degrees Celsius are the same, then we begin with
F = C. We can replace C with 95 ( F – 32 ) because they are equal.

FC

FF

=

=−^5

9

() 32

The LCD is 9.

995

9

32

995

9

32

95

FF

FF

F

=−







= 















−

=

()

()

(FF

FF

FF

FF

F

F

F

−

=−

=−

−−

=−

=−

32

95532

95160

55

4 160

160

4

)

()

==− 40

At –40 degrees Fahrenheit and degrees Celsius are the same.

PRACTICE

1. The daily charge for a small rental car is C = 18 + 0.35x, where x is the
   number of miles driven.
   (a) If the car was driven 80 miles, what was the charge for the day?
   (b) Suppose that a day’s bill was $39. How many miles were driven?


2. The profit obtained for a company’s product is given by P = 25x − 8150,
   where P is the profit in dollars and x is the number of units sold. How
   many units must be sold in order for the company to have a profit of
   $5000 from this product?


3. A salesman’s weekly salary is based on the formula S = 200 + 0.10s,
   where S is the week’s salary in dollars and s is the week’s sales level in
   dollars. One week, his salary was $410. What was the sales level for that
   week?

PRACTICE

1. The daily charge for a small rental car is