There is a slide

Given: The sides of the triangle are 15 m, 11 m and 6 m.
To find: Area painted in color
Explanation:

Perimeter of the triangular walls = sum of 3 sides 

Perimeter = 15 + 11 + 6 = 32 m

Semi perimeter of triangular walls(s) =

= 16 m

Using Heron’s formula,

Area of the advertisement = Area of triangle = 

where, s = semi perimeter of the triangle

a, b and c are the sides of the triangle

Therefore for the given triangle,

Area  =

         =

         =

         = √800 m²
   
         = √(20 × 20 × 2)

(Taking 20 outside the square root, as a pair is present in square root, we get,)

       
Thus the area of painted color is 20√2 m².