Russian multiplication

Multiplication by repeated doubling, also known as peasant multiplication. For example to multiply 17 by 13, double the 17 and halve the 13, and add the doubles that correspond to an odd number in the other column.

So
doubled and halved
doubled and halved
doubled and halved
adding up the numbers in the first column that correspond to an odd number in the second

17 × 13
34 × 6
68 × 3
136 × 1
(17 + 68 + 136) = 221

Related category

• ARITHMETIC

Also on this site:

Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History

BACK TO TOP