If I remember correctly the rules for minimum inheritance, it’s actually (n-1)/n of the inheritance has to be dedicated to the children, where ‘n’ is the number of children.

Each child is entitled to 1/n of that.

If I have 5 children, I have to give them 4/5 of the inheritance. Each one will have 1/5 of that 4/5.

And in the case of a sole child, she must receive 100% of 50% of the inheritance, at least.

OK. That makes more sense (except (n-1)/n=0 when n=1). In New Zealand too, you're required to give some inheritance to each of your children. There isn't a formula but lawyers seem to have observed that a minimum of about 10% each is acceptable.

In the U.S, it is ok to completely disinherit children. It has to be done so explicitly though.