let the distance of pillar is "r" from one end of the slab
So here net torque must be balance with respect to pillar to be in balanced state
So here we will have

here we know that
mg = 19600 N
Mg = 400,000 N
L = 20 m
from above equation we have



so pillar is at distance 10.098 m from one end of the slab
Blood
I learned this in anatomy, and I've taken it twice
If all the sides are equal, then it is an equilateral triangle. This means after walking 100 meters, you had to turn 1/3 of 180 degrees (because that's what the interior angles of the triangle add up to).
So, 180 * 1/3 = 60 degrees.
We aren't done yet.
60 degrees is not the angle which you have turned from your path.
You turned 120 degrees to describe an angle of 60 degrees on the interior side.
The answer is B.