Question

On-the-Go Phone Company has two monthly plans for their customers. The EZ Pay Plan costs $0.15 per minute. The 40 to Go Plan costs $40 per month plus $0.05 per minute.

Write an expression that represents that monthly bill for x minutes on the EZ Pay Plan.

Answer 1

Ok, the EZ plan can be written as:

C1(x) = $0.15*x

where x is the number of minutes used in the whole Month.

The 40 to Go Plan can be written as:

C2(x) = $0.05*x + $40.

So we have two linear relationships.

The Ez plan has a larger slope, but has no y-intercept.

So we now can find the number of minutes needed to have the exact monthly cost in each plan:

C1(x) = C2(x)

$0.15*x = $0.05*x + $40

($0.15 - $0.05)*x = $40

$0.10*x = $40

x = $40/$0.10 = 400.

So if in one month, you use exactly 400 minutes, you will pay exactly the same wich each plan.

Now, if you speak less than 400 minutes, is better to use the EZ Pay Plan, because it has o y-intercept, and is more efficient for lower values of x.

If you will use more than 400 minutes per month, then the 40 to Go Plan is better, because the slope is smaller.