College Physics
posted by Paige .
A freely rotating merrygoround on a playground has a moment of inertia of 312 kgm2 and a radius of R=2.5 m. It is rotating with ω0=2.8 rad/s when a kid of mass 45 kg is standing on its outer rim. Neglecting friction, what is going to be the angular velocity of the merrygoround after she walked d=0.7 m toward the center?

I before: 312
I after: 31245(2.5.7)^2
conservation of momentum applies
momentumbefore=momentum after
312wo=(31245(2.5.7)^2)wf
solve for wf 
So would I divide the problem by wf?