GeekDad Puzzle of the Week Solution – Jungle River Crossing

Reading Time: 2 minutes

This past week’s puzzle, recounting our recent tropical excursion:

As part of our recent jungle adventure (invented solely for the purposes of this puzzle), my wife Allison and our two children Max and Nora had to cross a river with our supplies to view a live volcano.

A low-res photo from our recent jungle excursion, courtesy (and property) of Activision.
A low-res photo from our recent jungle excursion, courtesy (and property) of Activision.

From a local canoe rental firm, we were able to lease a canoe, but the canoe had a strict weight limit: no more than 100kg of people or supplies could rest in the canoe at any point in time or it would sink instantly. This would not only forfeit our canoe-rental deposit, but would also feed the piranha that inhabit the river throughout its fast-running length.

Strictly for the purposes of this puzzle, my family has the following weights (ok, ok, masses):

Judd90kg
Allison80kg
Max60kg
Nora40kg
Supplies20kg

Please note that any/all people can row the canoe in either direction, that the supplies are indivisible, and that the canoe cannot be simply pushed to “coast” across the river due to the current.

Is it possible for us to devise a scheme to cross the river with our supplies to see the volcano? If so, how? If not, why not?

It turns out that it was possible for us to view the volcano as a family, with our supplies. The crossing went as follows:

  • Max and Nora row across, and Nora returns.
  • I (Judd) row across by myself, and Max returns.
  • Max and Nora row across, and Nora returns.
  • Allison rows across with the supplies, and Max returns.
  • Max and Nora row across, and everyone (including the canoe and the supplies) are on the far side.

Congratulations to Greg Hunt for submitting a correct response to this puzzle and being selected at random from among the correct (or reasonably correct) submissions received. A $50 Gift Certificate from the amazing team at ThinkGeek will be on its way!

Thanks to everyone that submitted an answer. Happy Puzzling!

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