I can’t answer because I don’t know the total area of the walls, if I have that I can help you
To solve this problem you must apply the proccedure shown below:
1- The ladder forms an isosceles triangle, because it has two equal sides.
2- Let's call the angle 
. To calculate it , you can divide the triangle into two equal right triangles and the angle will be divided into two equal parts too. Therefore, you can calculate the half of the angle and then multiply it by two, as following:
The answer is: 
2910:4
Fraction=1455/2 or 727 1/2
Decimal=727.5
7/8π
The circles have the same central angle measures; therefore, the ratio of the intercepted arcs is the same as the ratio of the radii.
4/7 = 1/2π over x
x = 7/8π
