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How often does a stopped clock show the right time? |
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We all know the answer to that one don't we?
It depends on the type of clock of course: it will be twice a day on a round analogue 12hr clockface, but only once on a digital 24hr display. The ten puzzles posed here concern only the round clockface as shown opposite, though a digital display is also provided. On this page they should simply show your current local time. The maths used is straightforward. There are a few facts and methods to be aware of though, so if unfamiliar with this type of puzzle you should first read the Basics page, then work through them in turn (they progress in difficulty), trying to work them out yourself before running a demo or checking the answers and maths. |
Demos start at midnight (00:00:00 hrs) and end with the final answer during that day, or else at 23:59:59. Click  to run.
The hands will pause briefly or stop on reaching the nearest second relevant to the answer(s) concerned. They can also be paused and restarted at any time with  , or reset to the beginning with  .
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A challenge |
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Some of the more difficult puzzles rely on certain judgments to be made, such as whether one angle is larger or smaller than another, less or more than 180° etc. While easy to decide mentally (and to program), it is interesting to find purely arithmetic ways to emulate such decision-making using only the simple maths operations covered by the Basics page.
I offer my own suggestions in the Extra maths sections of several puzzles, although those for puzzles 7 & 9 in particular seem seem rather over-complicated. Any better suggestions will therefore be welcome and added to the site. You may email me at jsmaje@gmail.com |
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