## Precalculus (6th Edition) Blitzer

(a) We know that the objective here is to determine the percentage of seniors who used alcohol in $2014$. As we observe the graph, the line that shows the percentage of people using alcohol, for the year 2014, corresponds to 68%. Therefore, the percentage of seniors who used alcohol in $2014$ is approximately equal to 68%. (b) In year 2014, the value of n will be as follows: \begin{align} & n=2014-1990 \\ & =24 \end{align} Let us consider the following given formula: $A=-0.9n+88$ So, after substituting $n=24$ in the above formula and we get: \begin{align} & A=-0.9n+88 \\ & =-0.9\left( 24 \right)+88 \\ & =-21.6+88 \\ & =66.4 \end{align} Therefore, the percentage of seniors who used alcohol in $2014$, calculated by using the formula is 66.4%. This value is almost equal to the value obtained through the graph, which is 68%. . (c) We know that the objective here is to determine the percentage of seniors who used marijuana in $2014$. As we can see from the given graph, the line that shows the percentage of people using marijuana, for the year $2014$, corresponds to 44%. Therefore, the percentage of seniors who used marijuana in $2014$ is approximately equal to 44%. (d) In year 2014, the value of n will be as follows: \begin{align} & n=2014-1990 \\ & =24 \end{align} Now, let us consider the given formula: $M=0.1n+43$ So, after substituting $n=24$ in the above formula, we get: \begin{align} & M=0.1n+43 \\ & =0.1\left( 24 \right)+43 \\ & =2.4+43 \\ & =45.4 \end{align} Therefore, the percentage of seniors who used marijuana in $2014$, calculated by using the formula is 45.5%. This value is almost equal to the value obtained through the graph, which is 44%. (e) We know that the objective here is to determine the year in which alcohol consumption was maximum. As we can observed from the given graph, the point where the percentage is maximum, can be seen as for the year 1990. The value of the percentage is 90%. Therefore, the percentage of seniors having maximum consumption of alcohol was in the year $1990$ and was approximately equal to 90%.