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Programming Enigma Puzzles

5 September 2012

Posted by on **From New Scientist #2881, 8th September 2012** [link]

The penny-farthing was a precursor to the modern bicycle. It had one very large wheel with pedals, over which was the saddle, and one much smaller trailing wheel to enable steering. We have some very early film of my great-grandfather riding one he had built. It had a large wheel 6 metres in circumference with 48 spokes, and a small one of one-third that diameter having 20 spokes. It had no brakes. He was hurtling downhill – luckily at less than 50 km/h – and just before he fell off, the film appears to show both wheels not rotating. If the film is showing 16 frames per second how fast, in kilometres per hour, was he then travelling?

[enigma1714]

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If I understand the puzzle correctly, it is fairly straightforward to solve…

Solution:The penny-farthing was travelling at 28.8 km/h.Here’s a simple Python program to compute the solution using the

fractionsmodule.I’d already solved this with just pencil and paper (not even a calculator).

Why did someone publish the solution?

I thought this was not allowed. It certainly isn’t ‘cricket’….

I normally try to avoid disclosing the answer explicitly on my comments (until the deadline for entries has passed), but with a puzzle this straightforward it’s difficult to talk about the solution in a way that doesn’t disclose it.