Physics Angular Velocity Bullet Question?

Hello,

I'm attempting to study for Physics, but I'm stuck on another problem:

A bullet of mass m = 20 gm [It says gm, I'm assuming it just means grams, so in kg = .02] is traveling at a velocity of 200 m/s perpendicular to the long axis of a wood block resting on a frictionless surface. The mass of the block is M = 10kg, and its length is L = 1 m. The bullet goes through the end of the block, emerging along its original path but with a reduced velocity of 100m/s.

Part b is just the easy conservation of momentum, mv of bullet = mv of bullet + mv block....

But part a is:

Determine the magnitude of the angular velocity of the block, assuming that the block is thin enough so that the moment of inertia about its center of mass is Icm = (1/12)ML^2.

I didn't really know how to do this, but I tried:

200m/s * .02 = 100m/s * .02 + 1/12 * 10 * 1^2 * omega

2 = 10/12 omega

2.4 = omega

The answer is, however, that omega = 1.2, which is half of my answer. Am I missing a 1/2 somewhere, or is this just a coincidence and I did everything totally wrong?

Thanks!