SOLUTION: ANASTACIA HAS A CHOICE BETWEEN TWO CELL PHONE PLANS, ONE PLAN HAS UNLIMITED MINUTES FOR A FLAT FEE OF $60 PER MONTH. THE OTHER PLAN IS $15 PER MONTH PLUS 30 CENTS. ANASTACIA CHOOSE

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Question 30444: ANASTACIA HAS A CHOICE BETWEEN TWO CELL PHONE PLANS, ONE PLAN HAS UNLIMITED MINUTES FOR A FLAT FEE OF $60 PER MONTH. THE OTHER PLAN IS $15 PER MONTH PLUS 30 CENTS. ANASTACIA CHOOSES THE PLAN WITH THE FLAT FEE OF $60 PER MONTH SO HOW MANY MINUTES DOES ANASTACIA PLAN ON USING HER PHONE EVERY MONTH?
Answer by mbarugel(146) (Show Source):
You can put this solution on YOUR website!
Let's call X to the number of minutes Anastacia plans to use. If Anastacia takes the other plan, then the total fee she will pay is , because she will pay $15 plus $0.30 per minute.
Anastacia has chosen the $60 flat fee plan. That is because she expected this plan to be cheaper then the other one. So we have the inequality:

So, solving for X,

We conclude that she is planning to use more then 150 minutes. If she planned to use less than that, then she should have chosen the non-flat plan