algebra 1 or 2 question

Question

The phone company NextFell 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 150 minutes, the monthly cost will be $100.5. If the customer uses 780 minutes, the monthly cost will be $384.

A) Find an equation in the form y=mx+b,y=mx+b, where xx is the number of monthly minutes used and yy is the total monthly cost of the NextFell plan.

y=

 

B) Use your equation to find the total monthly cost if 601 minutes are used.

Answer: If 601 minutes are used, the total cost will be :

Answer 1

Hi Grace,

A) The equation will be :

y= 0.45x +33

You can find the slope 0.45 by using the two "points" given in the problem and then use that slope to find the y-intercept as follows:

Slope m= ($384 - 100.50)/ (780 minutes - 150 )

m = 283.50/630= 0.45

Then using one of the "points" , substitute the coordinates into your equation to find b, the y-intercept. I will use 780 minutes, $384:

y=mx + b

384= 0.45 * 780 + b

384 =351 + b

b= 33

Equation: y = 0.45x + 33

B) Use your equation to find the total monthly cost if 601 minutes are used.

Answer: If 601 minutes are used, the total cost will be  $303.45:

y =0.45 * 601 + 33

y= 270.45 + 33

y= $303.45

Be happy to help with lessons/tutoring if you are in need now or in the future.

Take care,

Irene Rooney