Mathematician Johnny Ball, in the online show Numberphile, described what Western culture calls "multiplication in Russian." He learned this name while still a schoolboy, and only many years later, while studying the history of mathematics, he found out that the birthplace of the algorithm, in fact, is Ancient Egypt. At different times it was called "peasant counting" or "the method of halves and doublings."
Multiplication in Russian works for any integer values and can be easily checked by rearranging them. The calculation order is as follows:
- We write the first number in the left column, the second in the right one;
- Decrease the value in the left column by half at each step until we reach "1". If fractional numbers come across, just discard the fractional part;
- Opposite each line in the left column in the right column, write the doubled value of the previous number from this column;
- Delete lines with even numbers on the left;
- Add the remaining numbers in the right column and get the answer.
The method originated in ancient Egypt, because even then it became necessary to multiply large numbers. For example, how much will the consumption of flat cakes and jugs of beer increase if the detachment of workers is strengthened by a group of fifty people? Even a child can take half or double the numbers, these are the simplest operations, plus with this method there is no need to process large arrays of intermediate data.