SOLUTION: The cost of a long distance telephone call is determined by a flat fee for the first 5 minutes and a fixed amount for each additional minute. If a 15 minute telephone call costs $3

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Question 302230: The cost of a long distance telephone call is determined by a flat fee for the first 5 minutes and a fixed amount for each additional minute. If a 15 minute telephone call costs $3.25 and a 23 minute call costs $5.17, find the cost of a 30 minute call.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The cost of a long distance telephone call is determined by a flat fee for the
first 5 minutes and a fixed amount for each additional minute.
If a 15 minute telephone call costs $3.25 and a 23 minute call costs $5.17, find the cost of a 30 minute call.
:
Let x = flat fee for 5 min
Let y = per minute fee after 5 min
:
cost of 15 min call equation
x + 10y = 3.25
:
Cost of 23 min call equation
x + 18y = 5.17
:
Subtract the 1st equation from the 2nd equation
x + 18y = 5.17
x + 10y = 3.25
------------------subtraction eliminates x, find y
8y = 1.92
y = 1.92%2F8
y = $.24 for each minute over five minutes
Find y
x + 10y = 3.25
x + 10(.24) = 3.25
x + 2.40 = 3.25
x = 3.25 - 2.40
x = $.85 flat fee for 1st five minutes
:
Cost for a 30 min call
C = .85 + 25(.24)
C = $6.85