Modeling

Using Linear Systems

Example

Anne is trying to choose between two phone plans. The first plan, with Vendafone costs $20 per month, with calls costing an additional 25 cents per minute. The second company, Sellnet, charges $40 per month, but calls cost only 8 cents per minute. Which should she choose?

Step 1. Write an equation for each plan.

y = total cost of the plan and x = number of minutes

Vendafone: y = 0.25x + 20

Sellnet: y = 0.08x + 40

Step 2. Solve the system of equations using one of the methods discussed earlier.

The following is a graph representing the situation.

Cost Per Month Graph

The intersection point is (117.65, 49.41)