19+34+21+10+6=? 19+34+21+10+6=\text{?} 19+34+21+10+6=?
In order to simplify our calculations, we try to add numbers that give us a round result.
Keep in mind that:
19+21=40 19+21=40 19+21=40
34+6=40 34+6=40 34+6=40
Now, we get a more manageable exercise to solve:
40+40+10=80+10=90 40+40+10=80+10=90 40+40+10=80+10=90
90