Minority Interest

Can anyone please tell me an easy way to calculate minority interest. Preferably a formula.

I found this: https://www.analystforum.com/forums/cfa-forums/cfa-level-ii-forum/9998121

but I am not sure why they are multiplying with Net Income.

Particularly for partial goodwill.

Preferably a formula to calculate minority interest for partial goodwill.

Full goodwill: NCI value = (NCI%) x (fair value of the subsidiary)

Partial goodwill: NCI value = (NCI%) x (fair value of the subsidiary’s identifiable net assets)

Thanks so much!