Suppose that the monthly cost of a long-distance phone plan (in dollars) is a linear function of the total calling time (in minutes). When graphed, the function gives a line with a slope of 0.13.
The monthly cost for 42 minutes of calls is $16.18 . What is the monthly cost for 47 minutes of calls?
2006-10-29 02:58:05 · 3 answers · asked by SCHNITZEL 1 in Science & Mathematics ➔ Mathematics
The slope is what is making this one seem difficult,
I get $19.26 for 47 minutes, but, I am not certain where the slope comes in?
2006-10-29 03:09:51 · update #1
The equation of a line is y = mx + b and you know m (from the problem) to be .13 so knowing one set of time and cost numbers, you calculate the 'b' value as
1618 = .13*42 + b => b = 1618 - .13*42 = 1612.54 and the equation is
y = .13*x + 1612.54 so 47 minutes of calls would be
y = .13*47 + 1612.54 = 1618.65 or $16.19 (rounded to the nearest penny)
Doug
2006-10-29 03:09:31 · answer #1 · answered by doug_donaghue 7 · 0⤊ 0⤋
If is linear, you can solve applying conversion factors:
47 minutes *($ 16.18/ 42 minutes)
Use your calcultor and get the cost.
2006-10-29 11:04:41 · answer #2 · answered by jaime r 4 · 0⤊ 0⤋
Cost= slope* minutes + constant
16.18= 42*0.13+constant
=>constant=10.72
newcost= 47*0.13+ 10.72
=>cost for 47 minutes=16.83
2006-10-29 11:13:19 · answer #3 · answered by AlexisEd 2 · 0⤊ 0⤋