59.--A PUZZLING WATCH.

From Amusements in Mathematics by Henry Ernest Dudeney.

If the 65 minutes be counted on the face of the same watch, then the problem would be impossible: for the hands must coincide every 65+5/11 minutes as shown by its face, and it matters not whether it runs fast or slow; but if it is measured by true time, it gains 5/11 of a minute in 65 minutes, or 60/143 of a minute per hour.

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59.--A PUZZLING WATCH.: Amusements in Mathematics by Henry Ernest Dudeney | amphi