Russian Multiplication

This is a short article which describes a different way to multiply two numbers.

All you need to do is divide by two, double a number, and add a column, and know how to recognize even and odd. Using these simple tools, you can multiply any two numbers.

Here is the method by example.

Step 1 Lay out your numbers as the first in two columns. e.g. 35 and 7

35 7

Step 2

Halve the first column and throw away the remainder. Keep doing this until you get to 1.

35 7
17
 8
 4
 2
 1

Step 3

Repeatedly double the other column

35    7
17   14
 8   28
 4   56
 2  112
 1  224

Step 4

Identify all rows where there are odd numbers in the left hand column:

35    7
17   14
 8   28
 4   56
 2  112
 1  224

Step 5

For each of the numbers in the right column where there is an odd number in the left column, add them up.

  7
 14
224
---
245

Now check your answer by casting out nines. (Link)

Or find out how to instantly square a number ending in 5.

Learn about Binary and Hexadecimal too.