*Answer:* Neglecting any friction between the skates and the ice, we
expect the skater to spin with constant angular momentum. The skater's initial
angular momentum is

where is the skater's initial moment of inertia. The skater's final angular momentum is

where is the skater's final moment of inertia, and is her final angular velocity. Conservation of angular momentum yields , or

Now, we are told that . Hence,

Richard Fitzpatrick 2006-02-02