200.96=4*3.14*r^2

Solution for 200.96=4*3.14*r^2 equation:

Simplifying
200.96 = 4 * 3.14r2

Multiply 4 * 3.14
200.96 = 12.56r2

Solving
200.96 = 12.56r2

Solving for variable 'r'.

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

Add '-12.56r2' to each side of the equation.
200.96 + -12.56r2 = 12.56r2 + -12.56r2

Combine like terms: 12.56r2 + -12.56r2 = 0.00
200.96 + -12.56r2 = 0.00

Add '-200.96' to each side of the equation.
200.96 + -200.96 + -12.56r2 = 0.00 + -200.96

Combine like terms: 200.96 + -200.96 = 0.00
0.00 + -12.56r2 = 0.00 + -200.96
-12.56r2 = 0.00 + -200.96

Combine like terms: 0.00 + -200.96 = -200.96
-12.56r2 = -200.96

Divide each side by '-12.56'.
r2 = 16

Simplifying
r2 = 16

Take the square root of each side:
r = {-4, 4}