Scratch Method

Latest update to this document: 1 October 2003



The Scratch Method Algorithm


(1) Every time a sum of ten is reached the number is scratched.
(2) The scratch can also occur in the hundreds, thousands, and so on.

5

+

1

0

2

5

_______

3

0

(/3 make 3 a 4)

_______

4

0



Using the left-to-right algorithm, 30 was attained by adding the tens column. The next step is to add the ones column.
The ones column value is equal to 10. To add the ten, you scratch 3 (which is in the tens value place)to obtain
a value of 4 (one more ten then the orginal 3). Then when added the value is 40.


Extra Practice Problems


Scratch Method Practice Problems


Addition Links

Partial Sums

Left-to-Right Addition

Addition Home Page


Links

DeGabriele Link Page

CS255 Computers in El Ed Home Page

Northern Michigan University


DeGabriele: adegabri@nmu.edu