Question

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 51 minutes of calls is $17.32 and the monthly cost for 79 minutes is $20.96. What is the monthly cost for 66 minutes of calls? Please add a step-by-step explanation, if possible.

Answer 1

The a answer is $17.12

Answer 2

The monthly cost (in dollars) of a long-distance phone plan is a linear function, which means that the cost is proportional to the total calling time (in minutes). To calculate the monthly cost for 66 minutes of calls, we can use the following equation:

Cost = m * Minutes + b

Where m is the slope of the line, and b is the y-intercept. To find m and b, we can use the two given points: (51, $17.32) and (79, $20.96).

Using the slope formula: m = (20.96 - 17.32)/(79 - 51) = 0.44

We can then use the y-intercept formula: b = 17.32 - 0.44*51 = -4.64

Now we can plug in 66 for Minutes and solve for Cost: Cost = 0.44*66 - 4.64 = $17.12

Therefore, the monthly cost for 66 minutes of calls is $17.12.