Question

Philip uses his cellular phone only for local service.
One month he paid $32.50 for 250 minutes of service, and another month he paid $37.00 for 400 minutes of service. Assume a linear relationship exists between the cost and the number of minutes of service. How much will Philip pay for 500 minutes of service?

Answer 1

these are just two points:
x1 = 250, y1 = 32.50
x2 = 400, y2 = 37.00
Find the equation of the line

Answer 2

M = 5.50/150

Answer 3

Well done bahrom!

Answer 4

or M = 55/1500 = 11/300

Answer 5

now just use any of the points:
y - 37 = (11/300)(x-400).
Plug in x = 500
y-37 = (11/300)*(500-400)
y-37 = (11/300)*100
y-37 = 11/3
y = 11/3 + 37

Answer 6

y = 40.67