How much does it cost to paint a tringular surface of sides 6m 5m and 11m at the rate of 20 per m^

Since such a triangle is just a flat line, it costs zero to paint it.

To calculate the cost of painting a triangular surface, we first need to find the area of the triangle. The formula to calculate the area of a triangle is:

Area = (base * height) / 2

In this case, we have a triangle with sides measuring 6m, 5m, and 11m. To find the area, we need to determine the height. We can use the formula for the height of a triangle:

height = √(s * (s - a) * (s - b) * (s - c)) / base

Where:
- "s" is the semiperimeter equal to (a + b + c) / 2
- "a," "b," and "c" are the lengths of the sides of the triangle
- "base" is any one of the sides of the triangle

Let's calculate the height of the triangle before proceeding to find the area.