Question

The cost of printing the school newspaper is $500 for 800 copies and $620 for 1200 copies. If the printing cost is a linear function of the copies printed, how do you find the cost of printing 1500 copies?

Answer 1

Cost of printing `1500` copies is `$710`

Explanation:

This is a linear function, i.e obeys straight line equation:

Let y denotes cost in `$` and x denotes number of copies.

Slope `m= (620 -500)/(1200-800)= 120/400=3/10`

Equation of straight line is `y=mx+c or 500 = 3/10*800+c or 500 =240+c or c= 500-240=260`
Equation of straight line is `y = 3/10 x+260`

Check: `620 = 3/10*1200 +260 or 620 =360+260 or 620 =620`

Cost of printing `1500` copies is `y =3/10*1500+260 = 450+260 = $710` graph{3/10 x+260 [-1280, 1280, -640, 640]} [Ans]