900=4(3.14)r^2

Solution for 900=4(3.14)r^2 equation:

Simplifying
900 = 4(3.14) * r2

Multiply 4 * 3.14
900 = 12.56r2

Solving
900 = 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.
900 + -12.56r2 = 12.56r2 + -12.56r2

Combine like terms: 12.56r2 + -12.56r2 = 0.00
900 + -12.56r2 = 0.00

Add '-900' to each side of the equation.
900 + -900 + -12.56r2 = 0.00 + -900

Combine like terms: 900 + -900 = 0
0 + -12.56r2 = 0.00 + -900
-12.56r2 = 0.00 + -900

Combine like terms: 0.00 + -900 = -900
-12.56r2 = -900

Divide each side by '-12.56'.
r2 = 71.65605096

Simplifying
r2 = 71.65605096

Take the square root of each side:
r = {-8.46498972, 8.46498972}