This method works because it converts it to binary multiplication. We need even numbers so whenever we have an odd number we ignore a group of whatever we were multiplying it by, so we have to add it to the end.
Ideas taken from: https://mathcurious.com/2019/12/29/the-russian-multiplication-method/#:~:text=The%20Russian%20peasant%20multiplication%20method,multiplication%2C%20rather%20than%20base%2010.
I am intrigued, Christine! Can you elaborate on how this method converts things to binary multiplication? I'm missing that somehow. Very cool!
ReplyDeleteHi! The binary multiplication aspect is that the multiplier that gets divided by two until it reaches 1, can be written in terms of binary multiplication. In my example, the number 74... if you start at the bottom, the rows that are crossed out are 0's and the rows that are used to sum up the answers are 1's. You end up with 1001010. 1x2^6 + 1x2^3 + 1x2^1 = 74
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