A short introduction Cookie policy

Solution to: Cork in the Canal

If you have written down a full paper of mathematical formulas, you have been thinking too complicatedly...

It is obvious that the cork does not move relatively to the water (i.e. it has the same speed as the water). Therefore, if the swimmer is swimming away from the cork for half an hour (upstream), it will take him another half hour to swim back to the cork again. Because the swimmer is swimming with constant effort, his speed is constant relatively to the speed of the water. You can look at it as if the water in the river does not move, the cork does not move, and the swimmer swims a certain time away from the cork and then back. Consequently, in that one hour time, the cork has floated from 1 kilometer up stream to the bridge.

Conclusion: The water in the canal flows at a speed of 1 km/h.

back to the puzzle
Copyright © 1996-2017. RJE-productions. All rights reserved. No part of this website may be published, in any form or by any means, without the prior permission of the authors.
This website uses cookies. By further use of this website, or by clicking on 'Continue', you give permission for the use of cookies. If you want more information, look at our cookie policy.