SOLUTION: OOPPPSS! I no i said the last one was my last one but I cam across another one that I do not understand how to do correctly. Can you please help it is a word problem? A cellula

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: OOPPPSS! I no i said the last one was my last one but I cam across another one that I do not understand how to do correctly. Can you please help it is a word problem? A cellula      Log On


   

Question 144142: OOPPPSS! I no i said the last one was my last one but I cam across another one that I do not understand how to do correctly. Can you please help it is a word problem?
A cellular phone company offers a contract for which the cost C, in dollars, of t minutes of telephoning is given by C=0.25(t-400) + 44.95 where it is assumed that t>_400 minutes. What times will keep cost between $91.20 and $114.70.
HELP PLEASE!!!
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
C=0.25%28t-400%29+%2B+44.95 Start with the given equation


91.20%3C=0.25%28t-400%29+%2B+44.95%3C=114.70 Set the right side greater than or equal to than the lower endpoint, but less than or equal to the higher endpoint



91.20%3C=0.25t-100+%2B+44.95%3C=114.70 Distribute


91.20%3C=0.25t-55.05%3C=114.70 Combine like terms


146.25%3C=0.25t%3C=169.75 Add 55.05 to all sides


585%3C=t%3C=679 Divide all sides by 0.25 to isolate t


So if the time is between 585 and 679 minutes, then the cost will be between $91.20 and $114.70.