Circumference and Pi

$\frac{C_A}{R_A}=\frac{C_B}{R_B}$

$C_A \times C_B=R_A\times R_B$

$\frac{C_A}{C_B}=\frac{R_A}{R_B}$

$C_A \times R_A=C_B\times R_B$

None of the above.