Answer
$A=96.0~cm^{2}$
$P=48.0~cm$
Work Step by Step
To find the area, we use Heron's formula.
We have the sides:
$a=12cm$
$b=16cm$
$c=20cm$
Thus:
$s=\frac{1}{2}$$(a+b+c)=\frac{1}{2}(12+16+20)$
$s=24cm$
and the area is:
$A=\sqrt {s(s-a)(s-b)(s-c)}$
Thus:
$A=\sqrt {24cm(24cm-12cm)(24cm-16cm)(24cm-20cm)}$
$A=96.0~cm^{2}$
To find the perimeter, we add the lengths of all the sides:
$P=12cm+16cm+20cm=48.0~cm$
