Constant angular acceleration problem

[Paulhaley2000]

Ok so here is the problem

A centrifuge operates at 3600 rpm. When switched on it rotates 72 times before reaching operational angular speed. Find the constant angular acceleration while its speeding up.

Ok so I already know I needed to convert rpm to rad/sec which I did. I'm stuck here because the formula I have for ang acc is (Change in W)/ time. But I don't know time or ang acc. Thanks for the help btw

 

[tms]

You don't know the time, but you do know the "distance". The solution is analogous to linear motion in 1 dimension.