Answer:
Ok you're talking about "PI"
Area of a circle:
πr^2
What that basically means is
π <- That sign is 3.14
You wanna times that with the radius (r).
The radius is half of the diamater so divde the diameter by 2 then mutiply whatever u get with 3.14
Then the final step is do 3.14 x radias then times 2.
That's it :D
Hope this helps ~