Angle can be measured in two units. Radians and degrees.
In radians, $\pi$ means half circle as $2*\pi*r$ represents the circumference of whole circle. Thus this unit can be easily justified.
But I am curious about degrees. Why a circle has only 360 degrees? Why not 1000 degrees. A quarter circle can have 250 degrees. Is it just a convention like Kg or metre, or there is some reason for choosing 360 degrees.
I hope I am clear with my question. If you want more details about what I am asking, let me know.