Problema Solution
lisa can not remember which long distance plan she has with her phone company. however she knows that she pays a basic monthly fee and a rate per minute for long distance calls. in June her bill was &58.3 for 115 minutes of long distance calls and in July is was $86.29 for 426 minutes
A) Express the monthly cost, C as a function of x, the number of minutes of long distance calls made.
B) what will the monthly cost be in August if she makes 347 minutes of long distance calls?
Answer provided by our tutors
we interpret "her bill was &58.3 for 115 minutes" to be "her bill was $58.3 for 115 minutes"
let 'b' represent the basic monthly rate and 'r' her rate per long distance minute
cost per month, 'x' represents the number of long distance minutes:
C = rx + b
we have this system of equations based on the June and July bills:
58.3 = 115r + b
86.29 = 426r + b
solving this system we have:
r = 47.95
b = 0.09
cost in August with 347 minutes of long distance calls:
C = 347(0.09) + 47.95 = 79.18
Lisa's August bill would be $79.18