SOLUTION: The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 30 minutes of calls is $15.46 and the
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Question 174364: The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 30 minutes of calls is $15.46 and the monthly cost for 84 minutes is $20.32. What is the monthly cost for 54 minutes of calls?
Found 2 solutions by stanbon, Mathtut:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 30 minutes of calls is $15.46 and the monthly cost for 84 minutes is $20.32. What is the monthly cost for 54 minutes of calls?
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You have two points: (30,15.46) and (84,20.32)
slope = (20.32-15.46)/(84-30) = 4.86/54 = 0.09
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intercept ?
Form : y = mx + b; solve for "b":
15.46 = 0.09*30 + b
b = 12.76
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Equation:
cost = 0.09(minutes) + 12.76
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If minutes is 54 you get,
c(54) = 0.09*54 + 12.76
c(54) = $17.62
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Cheers,
Stan H.
Answer by Mathtut(3670) (Show Source): You can put this solution on YOUR website!
we have 2 points (30,15.46) and (84,20.32)
:
slope = 20.32-15.46/84-30=4.86/54=.09
:
y-15.46=.09(x-30)
:
y-15.46=.09x-2.7
:
.09x-y=-12.76
:
x=54
:
.09(54)-y=-12.76
4.86-y=-12.76
:
dollars
:
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