Answer
a) 50%
b) 51%; overestimate; 1%
c) 22%
d) 21%; it is slightly lower than the estimate in part c
e) 1980; 72%
Work Step by Step
a) Looking at the respective line graph, the percentage of seniors who used alcohol in 2000 was 50%.
b) The year 2000 occurred 20 years after 1980, so $n$ will have a value of 20 in the model displaying the percentage of seniors using alcohol: -0.9(20) + 69 = 51%. This is higher than the graph value of 50%, so the model overestimates the actual value by 1%.
c) The graph value for the line depicting seniors using marijuana seems to be around 22% in the year 2000 (estimations might fluctuate above or below this value by 1%).
d) The year 2000 occurred 20 years after 1980, so $n$ will have a value of 20 in the model displaying the percentage of seniors using marijuana: -0.3(20) + 27 = 21%. This is slightly lower than the value depicted by the graph (answers might fluctuate depending on the estimation in part c).
e) In 1980, alcohol use by seniors was the highest with an estimated percentage of 72%. Look at the line that portrays the percentage of seniors using alcohol and find the highest point on that line.
