We measure the radius r of a circle and obtain that that r=9 centimeters. We use this value to compute the area of the circle. We know that the error in our measurement is at most 1.6%. Use the linear approximation to the area A(r)=pi*r^2, at r=9 to estimate the maximum error in our computed value for the area.

I get (162/125) * pi as my answer. :/

Is the equation not 2 * pi * 9 * .016?