Inequalities and Equalities

Question

An internet provider charges $30 per month for 1000 minutes of DSL service plus $0.025 cents for each additional minute. In a one year period the customer's bill ranged from $35.40 to $49.20. What were the least most and least minutes used?

Answer 1

C = 30(m/1000) + .025(m-1000) when m>1000, e=excess over 1000 minutes

35.40 - 30= 5.4 = +.025(e)

e =5.4/.025 = 216 over 1000

m= 1216 minutes

49.20 -30 = 19.2 = .025e

e = 19.2/.025 = 768

m= 1768

1,216 < minutes < 1,768