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 ________ $m^{2}$ .

5√5

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12√5

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Solution

The correct option is C
12√5

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

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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 ________ m2.

The correct option is C 12√5 Semi-perimeter of a triangle, s = a+b+c2 where a, b and c are the sides of the triangle. s=7+8+92=242=12 m Area of a triangle, A = √s(s−a)(s−b)(s−c) =√(12)(12−7)(12−8)(12−9) =√(12)(5)(4)(3)=12√5 cm2

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 ________ $m^{2}$ .