I assume that you meant circumference instead of circumstance as circumstance is not a math term. 
Given that the circumference is 24,901, determine the diameter. 
So, when we find the circumference of a circle. We multiply the diameter by pi (3.14). 
However, if we want to find the diameter, we can reverse it by dividing by pi to get the diameter. 
So, it would become: 
D = C/pi 
D = 24901/3.14 
D = 7930.25
Thus, the diameter is 7,930.25 (insert units here).