math help please

Question

The cost C of printing a magazine is directly proportional to the number of pages N of the magazine. If an 18 page magazine costs 27 dollars to print, how much will a 45 page magazine cost to print?

Answer 1

The cost C of printing a magazine is directly proportional to the number of pages N of the magazine

TRANSLATES into C = kN.

 

Since when N = 18, C = 27, it follows that k =C/N = 27/18 = 1.5 $ per page.

 

Now when N = 45, C = 1.5•45 = $67.50