Question

The phone company A Fee and Fee 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
310 minutes, the monthly cost will be $68. If the customer uses 620 minutes, the monthly cost will
be $99.

A) Find an equation in the form y = mx + b, where x is the number of monthly minutes used and
y is the total monthly cost of the A Fee and Fee plan.
Answer: y =
B) Use your equation to find the total monthly cost if 980 minutes are used.
Answer: If 980 minutes are used, the total cost will be
dollars.

Answer 1

Answer:

The equation is:

• y = mx + b

We have two points:

• (310, 68) and (620, 99)

A)

Find the slope using these two points:

• m = (99 - 68)/(620 - 310) = 31/310 = 0.1

Use one of the points to find the y-intercept b:

• 68 = 0.1*310 + b
• 68 = 31 + b
• b = 68 - 31
• b = 37

The equation is:

• y = 0.1x + 37

B)

Find the value of y when x = 980:

• y = 0.1*980 + 37
• y = 98 + 37
• y = 135

The total cost is $135