200=3.14(r^2)

Solution for 200=3.14(r^2) equation:

Simplifying
200 = 3.14(r2)

Solving
200 = 3.14r2

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-3.14r2' to each side of the equation.
200 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
200 + -3.14r2 = 0.00

Add '-200' to each side of the equation.
200 + -200 + -3.14r2 = 0.00 + -200

Combine like terms: 200 + -200 = 0
0 + -3.14r2 = 0.00 + -200
-3.14r2 = 0.00 + -200

Combine like terms: 0.00 + -200 = -200
-3.14r2 = -200

Divide each side by '-3.14'.
r2 = 63.69426752

Simplifying
r2 = 63.69426752

Take the square root of each side:
r = {-7.980868845, 7.980868845}