Adding a list

MATH

How to add a list of numbers

*Add as usual
*find compliments (numbers that add up to ten)

Example:
9   ١
2   ٢
3   ٢
5   ٢
1   ١
__+
20

Everyone will agree that instead of adding from top to bottom it is faster to look for numbers that add up to ten. 9 & 1 is 10 and so is 5+2 & 3

2   ٣
9   ١
4   ٢
3   ٣
6    ٢
5   ٣
1   ١
_____+
30

Checking off compliments mentally with Eastern Arabic numerals or Hebrew letters may be useful