SOLUTION: When making a telephone call using a calling card, a call lasting 6 minutes costs $2.90. A call lasting 16 minutes cost $6.90. Find a linear function that relates the cost, C, of a

Question 336152: When making a telephone call using a calling card, a call lasting 6 minutes costs $2.90. A call lasting 16 minutes cost $6.90. Find a linear function that relates the cost, C, of a making a call length, X, of the call, treating length of the call as the independent variable.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
When making a telephone call using a calling card, a call lasting 6 minutes costs $2.90. A call lasting 16 minutes cost $6.90. Find a linear function that relates the cost, C, of a making a call length, X, of the call, treating length of the call as the independent variable.
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You have two points : (6,2.9) and (16,6.9)
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slope = (6.9-2.9)/(16-6) = 4/10 = 2/5
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Linear Form: cost = (slope)(length of call)+b
Solve for "b":
2.9 = (2/5)(6)+b
b = 2.9-(2/5)(6)
b = 0.5
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Equation:
cost = (2/5)x + (1/2)
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Cheers,
Stan H.
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