Question

if the area of a circle, a, is given as a function of its radius: ( a=pi r^{2} ), evaluate ( a(3 mathrm{in}) ).
0.9 in
9.4 in
3.1 in
28.3 in

Explanation:

Step1: Substitute \(r = 3\) into the formula

\(A(3)=\pi\times(3)^{2}\)

Step2: Calculate \((3)^{2}\)

\((3)^{2}=9\), so \(A(3) = 9\pi\)

Step3: Approximate \(\pi\approx3.14\)

\(A(3)\approx9\times3.14 = 28.26\approx28.3\) (rounded to one - decimal place)

Answer:

28.3 in.