Enigmatic Code

Programming Enigma Puzzles

Puzzle #33: The mountain pass

From New Scientist #3259, 7th December 2019 [link] [link]

Aaron has spent the night camped at the foot of a mountain, while Bonnie camped at the summit. In the morning, Bonnie sets off down the path to base camp at exactly the same time as Aaron begins his ascent.

At midday they pass each other and nod a greeting, both of them maintaining their constant walking pace. Bonnie gets to the bottom at 4pm and sets up camp, but it isn’t until 9pm that Aaron finally reaches the top.

What time did the two hikers set off in the morning?

[puzzle#33]

One response to “Puzzle #33: The mountain pass

  1. Jim Randell 7 December 2019 at 8:11 am

    A spends x hours walking before noon (on the lower part of the mountain), and 9 hours walking after noon (on the upper part of the mountain).

    B spends x hours walking before noon (on the upper part of the mountain), and 4 hours walking after noon (on the lower part of the mountain).

    They each walk at a constant rate, so the ratios upper : lower will be the same for both.

    9 / x = x / 4
    x² = 36
    x = 6

    Solution: They both set off at 6am.

    So the upper part of the mountain takes 1.5× longer than the lower part.

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