Point to be present exactly at midway between center and circumference of circle (let’s say radius = r) should lie at circumference of circle of radius r/2.
Favorable outcome = 2*pi*r/2
Total outcome = Point can be anywhere inside the circle of radius r = Area of circle = pi * r * r
Probability = (2*pi*r/2) / pi * r* r = 1/r.
Not completely sure about correctness . Waiting for comments to verify.