1005.3=3.14r^2(20)

Solution for 1005.3=3.14r^2(20) equation:

Simplifying
1005.3 = 3.14r2(20)

Reorder the terms for easier multiplication:
1005.3 = 3.14 * 20r2

Multiply 3.14 * 20
1005.3 = 62.8r2

Solving
1005.3 = 62.8r2

Solving for variable 'r'.

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

Add '-62.8r2' to each side of the equation.
1005.3 + -62.8r2 = 62.8r2 + -62.8r2

Combine like terms: 62.8r2 + -62.8r2 = 0.0
1005.3 + -62.8r2 = 0.0

Add '-1005.3' to each side of the equation.
1005.3 + -1005.3 + -62.8r2 = 0.0 + -1005.3

Combine like terms: 1005.3 + -1005.3 = 0.0
0.0 + -62.8r2 = 0.0 + -1005.3
-62.8r2 = 0.0 + -1005.3

Combine like terms: 0.0 + -1005.3 = -1005.3
-62.8r2 = -1005.3

Divide each side by '-62.8'.
r2 = 16.00796178

Simplifying
r2 = 16.00796178

Take the square root of each side:
r = {-4.000995099, 4.000995099}