Question

The phone company splint has a monthly cellular plan where a customer pays a flat monthly fee and then a certain amount of money per minute used on the phone. If a customer uses 360 minutes the monthly cost will be $183. If the customer uses 630 minutes the monthly cost will be $304.50.
Find the equation for the monthly cost in dollars

Answer 1

Answer: y = 0.45x + 21

Step-by-step explanation:

let x represent the number of minutes used in a month.

Let y represent the monthly cost for x minutes.

If we plot y on the vertical axis and x on the horizontal axis, a straight line would be formed. The slope of the straight line would be

Slope, m = (304.5 - 183)/(630 - 360)

m = 121.5/270 = 0.45

The equation of the straight line can be represented in the slope-intercept form, y = mx + c

Where

c = y intercept

m = slope

To determine the y intercept, we would substitute x = 360, y = 183 and m = 0.45 into y = mx + c. It becomes

183 = 0.45 × 360 + c

183 = 162 + c

c = 183 - 162

c = 21

The equation for the monthly cost is

y = 0.45x + 21