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 36 minutes of calls is $17.53 and the

Algebra ->  Finance -> 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 36 minutes of calls is $17.53 and the       Log On


   

Question 1148592: 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 36 minutes of calls is $17.53 and the monthly cost for 75 minutes is $21.82. What is the monthly cost for 59 minutes of calls?
Found 2 solutions by josgarithmetic, josmiceli:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
x minutes    y cost
    36         17.53
    59          ?
    75         21.82

price %2821.82-17.53%29%2F%2875-36%29=0.11

point-slope form, y-17.53=0.11%28x-36%29

highlight%28y=0.11%28x-36%29%2B17.53%29
substitute x with 59 to find the asked cost.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
You are given 2 points on the straight line
( 36, 17.53 )
( 75, 21.82 )
Let +C+ = Monthly cost of plan
Let +t+ = calling time in minutes
You can use the general point-slope formula
+%28+C+-+17.53+%29+%2F+%28++t+-+36+%29+=+%28+21.82+-+17.53+%29+%2F+%28+75+-+36+%29+
+%28+C+-+17.53+%29+%2F+%28++t+-+36+%29+=+4.29+%2F+39+
+%28+C+-+17.53+%29+%2F+%28++t+-+36+%29+=+.11+
+C+-+17.53+=+.11t+-+3.96+
+C+=+.11t+%2B+13.57+
-----------------------------
+t+=+59+ min
+C+=+.11%2A59+%2B+13.57+
+C+=+6.49+%2B+13.57+
+C+=+20.06+
$20.06 per month
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