To find the monthly cost for 50 minutes of calls on a linear phone plan with a rate of $0.09 per minute, use the point-slope form of a line. With the information given, the monthly cost for 50 minutes is $17.40.
The student has asked to determine the monthly cost for 50 minutes of calls given that the monthly cost is a linear function of the total calling time, with a slope of $0.09 per minute and that the cost for 46 minutes is $17.04.
To solve this, we use the point-slope form of the linear equation, which is y - y1 = m(x - x1), where m is the slope and (x1, y1) is a known point on the line. In this case, x1 is 46, y1 is $17.04, and the slope m is $0.09.
Using this information, we get: y - 17.04 = 0.09(x - 46). Plugging in x = 50 minutes, the equation becomes y - 17.04 = 0.09(50 - 46), which simplifies to y - 17.04 = 0.09(4), and then y - 17.04 = $0.36.
Adding $17.04 to each side gives us y = $17.40. Therefore, the monthly cost for 50 minutes of calls is $17.40.