My math strategys

This strategy is called tidy numbers.

What you need to do is if you get number like this 29+21 you need to add on 1 to 29 and - 1 on 21 which makes 30 instead of 29 and 20 instead of 21 so that make 20+30=50

This is called adding ten and 1s

If you had 29+21 you have 20+20=40 9+1=10 and 40+10=50