47=4(3.14)(r*r)

Solution for 47=4(3.14)(r*r) equation:

Simplifying
47 = 4(3.14)(r * r)

Multiply r * r
47 = 4 * 3.14(r2)

Multiply 4 * 3.14
47 = 12.56r2

Solving
47 = 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.
47 + -12.56r2 = 12.56r2 + -12.56r2

Combine like terms: 12.56r2 + -12.56r2 = 0.00
47 + -12.56r2 = 0.00

Add '-47' to each side of the equation.
47 + -47 + -12.56r2 = 0.00 + -47

Combine like terms: 47 + -47 = 0
0 + -12.56r2 = 0.00 + -47
-12.56r2 = 0.00 + -47

Combine like terms: 0.00 + -47 = -47
-12.56r2 = -47

Divide each side by '-12.56'.
r2 = 3.742038217

Simplifying
r2 = 3.742038217

Take the square root of each side:
r = {-1.934434857, 1.934434857}