Write an equation, find constant proportionally, and how much the printing cost will be for 5000 copies of 92 pg magazine

Question

1. Printing Cost: The cost C of printing a magazine is jointly proportional to the number of pages p in
the magazine and the number of magazine m printed.
a) Write an equation that expresses this joint variation.
b) Find the constant of proportionality if the printing cost is $60, 000 for 4000 copies of a 120 page magazines.
c) How much would the printing cost be for 5000 copies of a 92 page magazine?

Answer 1

1) C = knp where C is the cost, n is the number of magazines, p is the number of pages, and k is a fixed number constant.

 

 

2) 60000 = k(4000)(120)

 

    60000 = k(480000)

 

   60000/480000 = k

 

   k = 1/8

 

3) C = (1/8)(5000)(92) = $57500