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 40 minutes of calls is $15.60 and the monthly cost for 62 minutes is $18.46. What is the monthly cost for 56 minutes of calls?
Q. 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 40 minutes of calls is $15.60 and the monthly cost for 62 minutes is $18.46. What is the monthly cost for 56 minutes of calls?
Identify Known Points: Step 1: Identify the known points and the variable to find.We know the cost for 40 minutes is $15.60 and for 62 minutes is $18.46. We need to find the cost for 56 minutes.
Calculate Slope: Step 2: Calculate the slope (rate of change) of the cost function.Slope m = (Change in cost) / (Change in minutes) = $$18.46−$15.60 / (62 - 40)\)m=$2.86/22=$0.13 per minute.
Use Point-Slope Form: Step 3: Use the point-slope form of the linear equation to find the equation of the line.Using the point (40,$15.60) and slope $0.13:Cost = $15.60+$0.13×(Minutes−40)
Substitute to Find Cost: Step 4: Substitute 56 for the minutes in the equation to find the cost for 56 minutes.Cost for 56 minutes = $15.60+$0.13×(56−40)Cost for 56 minutes = $15.60+$0.13×16Cost for 56 minutes = $15.60+$2.08Cost for 56 minutes = $17.68
More problems from Evaluate two-variable equations: word problems