Simon has shown me an interesting way to add, subtract and multiply in binary using what is called a Napier’s Checkerboard (or Napier’s Chessboard), something he learned from his new hero, mathematician James Tanton.

ADDITION: Let’s try adding 11 and 12.

SUBTRACTION: Subtract 11 from 23.

MULTIPLICATION: How much is 16 times 8?

Wait, what about multiplying numbers that aren’t powers of two? Like 11 times 5?

Then Simon tried something more challenging: 23 times 15.

And… “I think we’re going to overwhelm this machine”, Simon said.

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