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Question 1003717: One phone company advertises a flat rate of $0.07 per minute for long-distance calls. Your long-distance plan charges $5.00 per month plus a rate of $0.05 per minute. How many minutes do you have to talk each month so that your average cost is less than $0.07 per minute?
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! x = number of minutes.
you equation is 5 + .05*x < .07*x
subtract .05*x from both sides of this equation to get 5 < .07*x - .05*x.
simplify this to get 5 < .02*x
divide both sides of this equation by .02 to get 5/.02 < x
solve for x to get 250 < x
this is the same as x > 250.
your cost per call will be less than 7 cents a call when the number of calls is greater than 250.
for example:
when x = 200, 5 + .05*x = 5 + 10 = 15 / 200 = .075 per call.
when x = 250, 5 + .05*250 = 5 + 12.5 = 17.5 / 250 = .07 per call.
when x = 300, 5 + .05*300 = 5 + 15 = 20 / 300 = .067 per call.
any number of calls less than 250 results in a cost per call greater than .07
250 calls results in a cost per call exactly equal to .07.
any number of calls greater than 250 results in a cost per call less than .07.
you have to talk more than 250 minutes in a month for your cost per call to be less than .07.
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