Answer
$$\approx 1.625 \% $$
Work Step by Step
Re-write as: $dA=\pi \ b \ da+\pi a \ db $
$dA(10,16)=16\pi \ da+10\pi db $
Set $da=\pm 0.1 \\ db=\pm 0.1$
$\implies dA=\pm 26(\pi) (0.1)=\pm 2.6 \pi$
The estimated change in $A$ can be computed as $dA=|\dfrac{dA}{A} \times 100|=|\dfrac{2.6 \pi}{160 \ \pi} \times 100 | \approx 1.625 \% $
