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

Algebra ->  Graphs -> 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       Log On


   

Question 174355: 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?
Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!

We'll interpolate the given data to get monthly cost for 54 minutes, which represented by x:
system%2830minutes=15.46%2C54minutes=x%2C84minutes=20.32%29
%2830-54%29%2F%2830-84%29=%2815.46-x%29%2F%2815.46-20.32%29
%28-24%29%2F%28-54%29=%2815.46-x%29%2F-4.86, cross multiply
-24%28-4.86%29=-54%2815.46-x%29
116.64=-834.84%2B54x}
116.64%2B834.34=54x
54x=951.48 ------->cross%2854%29x%2Fcross%2854%29=cross%28951.48%2917.62%2Fcross%2854%29
highlight%28x=17.62%29, Monthly cost for 54 minutes.
Thank you,
Jojo