what is the angular acceleration of the pulley?

Question

A pulley with a radius of 38 cm has a moment of inertia of 35.5 kg*m². If the net torque acting on the pulley is 7 N*m, what is the angular acceleration of the pulley?

Answer 1

Angular acceleration is the ratio between torque and moment of inertia.

That is,

7 Nm / 35.5 kgm² = 0.197 s^-2

I do not understand why you are also given the radius.