Question

If the side of a triangle are 5 kilometres 6 and 7 then area of a triangle is

Answer 1

$s = \frac{a + b + c}{2} = \frac{5 + 6 + 7}{2} \\ = \frac{18}{2} = 9 \\ by \: heron \: formula \\area = \sqrt{s(s - a)(s - b)(s - c)} \\ = \sqrt{9(9 - 7)(9 - 6)(9 - 5)} \\ = \sqrt{9 \times 2 \times 3 \times 4} = \sqrt{216} \\ 6 \sqrt{6} {cm}^{2}$