Also called "Ethiopian multiplication." To multiply two numbers and , write and in two columns. Under , write , where is the floor function, and under , write . Continue until . Then cross out any entries in the column which are opposite an even number in the column and add the column. The result is the desired product. For example, for

Russian multiplication works because it implements binary multiplication:

1. If , accumulate .

2. Right-shift one bit.

3. If , exit.

4. Left-shift one bit.

5. Loop.

Portions of this entry contributed by Dave Zobel

Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, p. 44, 1986.

CITE THIS AS:

Weisstein, Eric W. and Zobel, Dave. "Russian Multiplication." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/RussianMultiplication.html