calculus functions and models

Question

suppose the revenue R from the sale of a product is directly proportional to the number of units x that are sold. Suppose also that the sale of 75 units earns a revenue of 1586.25. Find the revenue if 79 units are sold. 

Answer: $

Answer 1

Since R is directly proportional to x, R = kx for some constant, k.

 

We are given that R = $1586.25 when x = 75.

 

So, 1586.25 = 75k.   Therefore, k = 21.15

 

Thus, R = 21.15x

 

When x = 79, R = 21.15(79) = $1670.85