Question

A dance floor has to be built as a triangular glass platform with the dimensions 7 m, 8 m and 9 m. The total surface area of the glass required to build such a platform is equal to ________ $\sqrt{5}{m}^2$.

• A. 12

Answer 1

The correct option is A 12
$\text{Semi-perimeter of a triangle, s =}\frac{a+b+c}{2}$
where a, b and c are the sides of the triangle.
$s=\frac{7+8+9}{2}=\frac{24}{2}=12m$
$\text{Area of a triangle, A =}$
$\sqrt{s(s-a)(s-b)(s-c)}$
$=\sqrt{\left(12\right)(12-7)(12-8)(12-9)}$
$=\sqrt{\left(12\right)\left(5\right)\left(4\right)\left(3\right)}=12\sqrt{5}{m}^2$