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Simplifying
211.1336 = 4(3.14)(r * r)
Multiply r * r
211.1336 = 4 * 3.14(r2)
Multiply 4 * 3.14
211.1336 = 12.56r2
Solving
211.1336 = 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.
211.1336 + -12.56r2 = 12.56r2 + -12.56r2
Combine like terms: 12.56r2 + -12.56r2 = 0.00
211.1336 + -12.56r2 = 0.00
Add '-211.1336' to each side of the equation.
211.1336 + -211.1336 + -12.56r2 = 0.00 + -211.1336
Combine like terms: 211.1336 + -211.1336 = 0.0000
0.0000 + -12.56r2 = 0.00 + -211.1336
-12.56r2 = 0.00 + -211.1336
Combine like terms: 0.00 + -211.1336 = -211.1336
-12.56r2 = -211.1336
Divide each side by '-12.56'.
r2 = 16.81
Simplifying
r2 = 16.81
Take the square root of each side:
r = {-4.1, 4.1}
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