1696.5=3.1415*(r^2)*15

Solution for 1696.5=3.1415*(r^2)*15 equation:

Simplifying
1696.5 = 3.1415(r2) * 15

Reorder the terms for easier multiplication:
1696.5 = 3.1415 * 15r2

Multiply 3.1415 * 15
1696.5 = 47.1225r2

Solving
1696.5 = 47.1225r2

Solving for variable 'r'.

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

Add '-47.1225r2' to each side of the equation.
1696.5 + -47.1225r2 = 47.1225r2 + -47.1225r2

Combine like terms: 47.1225r2 + -47.1225r2 = 0.0000
1696.5 + -47.1225r2 = 0.0000

Add '-1696.5' to each side of the equation.
1696.5 + -1696.5 + -47.1225r2 = 0.0000 + -1696.5

Combine like terms: 1696.5 + -1696.5 = 0.0
0.0 + -47.1225r2 = 0.0000 + -1696.5
-47.1225r2 = 0.0000 + -1696.5

Combine like terms: 0.0000 + -1696.5 = -1696.5
-47.1225r2 = -1696.5

Divide each side by '-47.1225'.
r2 = 36.00190992

Simplifying
r2 = 36.00190992

Take the square root of each side:
r = {-6.000159158, 6.000159158}