The angular-momentum ledger is a checked product. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Angular momentum is inertia times spin rate

Inertia 6 times spin rate 4 gives angular momentum 24.

L=6×4=24 kgm2/sL=6\times4=24\ \mathrm{kg\,m^2/s}
Angular momentumInertia times spin rate sets L.r=1 mm=6 kgr=1 mI=6 kg*m^2omega=4 1/sL=24 kg*m^2/s

Spin rate is shown as per second

The spin label is 4 per second, not hertz or a hidden radian unit.

ω=4 per second\omega=4\ \mathrm{per\ second}
Angular momentumInertia times spin rate sets L.r=1 mm=6 kgr=1 mI=6 kg*m^2omega=4 1/sL=24 kg*m^2/s