> all of which are aaaaalmost doable in your head for 2 digits, but maybe not quite. You might be good at Mathematics, this is like a standard trick the averag

> all of which are aaaaalmost doable in your head for 2 digits, but maybe not quite. You might be good at Mathematics, this is like a standard trick the average student can do. There are lots of other approaches but the easiest one to do mentally is this.