Whether he’s filling the bathtub with water or routing electricity through resistors – Mike Schilli juggles mathematical formulas with the assistance of the Python SymPy package.

I still remember a traumatic event as an elementary school student: A weekend newspaper had set a logic puzzle for kids, the solution of which it promised to publish in the next issue a week later. It involved a bathtub with two taps: one of which filled the tub in 10 minutes, the other in 15. The question was how long would it take to fill the tub if both taps were turned on all the way.

As a little boy, I was absolutely sure that 10 plus 15 equals 25, which is 25 minutes. My father laughed and suggested that couldn’t be true, because two taps would fill the bathtub faster than one alone. The next weekend, I was initially triumphant, because there it was – printed in black and white in the following issue – the confirmation that 25 minutes was the correct solution.

But disillusionment followed one week later: After receiving angry reader comments, the newspaper had to admit that it had made a mistake, because it does not take 25 minutes, but only 6 minutes, to fill the tub with both taps. I nearly fell off my chair and decided at that point to become a famous columnist peddling logic puzzles.

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