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kottke.org posts about Johnny Ball

Russian Multiplication: A Different Way to Multiply

posted by Jason Kottke   Feb 24, 2020

I’ve loved math since I was a kid. One of the big reasons for this is that there’s always more than one way to solve a particular problem and in discovering those solutions, you learn something about mathematics and the nature of numbers.1

In this video, math fan Johnny Ball shows us a different method of multiplication. In Russian multiplication (also called Ethiopian multiplication and related to ancient Egyptian multiplication), you can multiply any two numbers together through simple addition and doubling & halving numbers. The technique works by converting the numbers to binary and turning it into an addition problem.

I loved learning about this so much that I scribbled an explanation out on a napkin at brunch yesterday to show a friend how it worked. We’re friends because she was just as excited as I was about it. (via the kid should see this)

  1. I’ve probably told this story here before, but for an assignment in a quantum mechanics class in college, we had to derive an equation using two different techniques. After much struggle at the whiteboard on a Saturday morning, a friend and I got the results of these two approaches to converge on the same answer and it felt like we had unlocked a deep secret to the universe.