First of all, we start with the input 
Then we double it: 
Then we add 5 to this result: 
And this is the output: 
The shaded areas add to 2/5 of the area of the circle, which is given by
A = πr²
Then the shaded area is ...
(2/5)A = (2/5)π(10 in)²
shaded area = 40π in²
All that you are doing is trying to fiigure out the Frequency of all the tally marks!!