Answer
$10\sqrt{3021}$
Work Step by Step
In order to use Heron's Formula we have to find the semiperimeter:
$s=\frac{1}{2}(a+b+c)$
$s=\frac{1}{2}(11+100+101)$
$s=\frac{1}{2}*212$
$s=106$
We can use Heron's Formula from here:
$A=\sqrt{s(s-a)(s-b)(s-c)}$
$A=\sqrt{106*(106-11)(106-100)(106-101)}$
$A=\sqrt{106*95*6*5}$
$A=\sqrt{302100}$
$A=10\sqrt{3021}$
$A\approx 549.64$