Problema Solution
The average local monthly U.S. cell phone bill decreased from $61.48 in 1993 to $47.70 in 1996. Find the average rate of change. Then estimate the average monthly bill in 1997.
Answer provided by our tutors
we take the year to be the independent variable (x) and cost to be the dependent variable (y)
the average rate of change:
(47.7 - 61.48)/(1996-1993) = -4.5933
the monthly bill is decreasing each year by an average of $4.59 per year
if we assume this linear relationship holds, then the cost in 1997 will be:
cost = -4.5933(1997-1993) + 61.48
cost = 43.10679
the estimate for average monthly bill in 1997 is $43.11