A phone company offers two monthly charge plans. In Plan A, the customer pays a monthly fee of $38 and then an additional 4 cents per minute of use. In Plan B, the customer pays a monthly fee of $20 and then an additional 7 cents per minute of use.

Question

For what amounts of monthly phone use will Plan A cost less than Plan B?
Use for m the number of minutes of phone use, and solve your inequality for m.

Answer 1

For Plan A, the cost equation is given by:
C(A) = 38 + 0.04m

For Plan B, the cost equation is given by:
C(B) = 20 + 0.07m

To find the amount of monthly phone use for which Plan A costs less than Plan B, we need to set up an inequality:

38 + 0.04m < 20 + 0.07m

Now we solve for m:

0.04m - 0.07m < 20 - 38
-0.03m < -18
m > -18 / -0.03
m > 600

Therefore, for monthly phone use greater than 600 minutes, Plan A will cost less than Plan B.