SOLUTION: Bart has two choices to make a long distance phone call. His two choices are:10-10-220 and AT&T. Using 10-10-220, the cost is 99 cents for the first twenty minutes, and 7 cents f

Question 389350: Bart has two choices to make a long distance phone call. His two choices are:10-10-220 and AT&T. Using 10-10-220, the cost is 99 cents for the first twenty minutes, and 7 cents for each additional minute. AT&T just charges 6 cents for each minute. After how many total minutes will it be less expensive to use AT&T? Assume the call is at least 20 minutes.
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
Let m = # minutes of call. By assumption, . Then we have to solve the equation
0.99 + (m - 20)0.07 = 0.06m,
0.99 + 0.07m - 1.4 = 0.06m,
-0.41 = -0.01m,
m = 41, total # minutes after which it be less expensive to use AT&T
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