Question

How do you solve for r in the formula a=pi r squared

Answer 1

To solve for y, all you have to do is just separate r from all of the others and make it equal to the rest of the equation. So first it was, a=pi*r squared. 
Divide by pi on each side, 
a/pi=r^2
Take the square root of each side;
square root of (a/pi) =r
and that's all
Hope this helps.