153.86=3.14*r^2

Solution for 153.86=3.14*r^2 equation:

Simplifying
153.86 = 3.14r2

Solving
153.86 = 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.
153.86 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
153.86 + -3.14r2 = 0.00

Add '-153.86' to each side of the equation.
153.86 + -153.86 + -3.14r2 = 0.00 + -153.86

Combine like terms: 153.86 + -153.86 = 0.00
0.00 + -3.14r2 = 0.00 + -153.86
-3.14r2 = 0.00 + -153.86

Combine like terms: 0.00 + -153.86 = -153.86
-3.14r2 = -153.86

Divide each side by '-3.14'.
r2 = 49

Simplifying
r2 = 49

Take the square root of each side:
r = {-7, 7}