Enigma 1138: Pedal power
5 December 2016
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From New Scientist #2294, 9th June 2001 [link]
Jane left the campsite and cycled north at her own steady speed. At the same time Mark left the campsite and cycled south at a speed one mile per hour faster than Jane.
An hour later I realised that they had left without their packed lunches. So, at my own steady speed of 10 miles an hour, I cycled after Jane, gave her a packed lunch, turned round and cycled after Mark, gave him a packed lunch, and then turned round and cycled back to the campsite.
The round trip took me 5 hours. How long would it have taken if I had cycled to Mark first and then to Jane?