Volume of 1st wooden ball
$V = \frac{4}{3}\pi(1^3)$
$V = \frac{4}{3}\pi ~ \text{ft.}^3$
Unit weight of the wood material
$\gamma = \dfrac{200}{\frac{4}{3}\pi} = 47.746 ~ \text{lb/ft.}^3$
For the 2nd wooden ball
$W = \gamma V$
$50 = 47.476(\frac{4}{3}\pi r^3)$
$50 = 200r^3$
$r = 0.62996 ~ \text{ft.}$
$d = 2r = 2(0.62996)$
$d = 1.2599 ~ \text{ft.}$ answer