
Help with a problem
Using this equation:
$\displaystyle f(A)=0.0197A^2+1.85A+9.90$
Where $\displaystyle f(A)$ is the percentage of Americans at age $\displaystyle A$ who say they do volunteer work.
a.) Estimate the percentage of 25yearold Americans who say they volunteer. Did you perform interpolation or extrapolation?
b.) Estimate the percentage of 16yearold Americans who say they volunteer. Did you perform interpolation or extrapolation?
c.) For what age do half of Americans say they volunteer?
d.) For what age is the percentage who say they volunteer the greatest? What is that maximum percentage?
MY ANSWERS
a.) 44.1 % extrapolation
b.) 35 % extrapolation
c.) 99 years old
d.) No clue!
Are my answers correct? And what is the answer for question D ?
Thanks in advance!

for your d, take note that your function is parabolic which opens downward and thus has a maximum point. find that point using any method you know..