All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Logic
Got a Minute? (Posted on 2003-09-10) Difficulty: 3 of 5
You have an infinite amount of timers, each is an hour long (they do not have dials on telling you how long they've been going - they just beep when the time is up). You can set it to double speed at any time, but you cannot set it back to normal speed (eg if you set it to double speed at the start it will last 30 minutes.

Using each timer only once, is it possible to time exactly 25 minutes?

If it is, what is the smallest number of timers you need to do this, and the quickest time you can acheive it?

No Solution Yet Submitted by Lewis    
Rating: 3.6000 (15 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
To infinity and beyond! | Comment 32 of 35 |
Can't find a finite solution but it's clear that you can get 60, 30, 15, 7.5, 3.75 etc minutes and the infinite sum of every other term starting after 15+7.5 is 25. ie 15+7.5+1.875+0.46875+..., however you would not only need infinite clocks but you would have to set infinite number going at the beginning and then later set an infinite number going infinitely often!
  Posted by Mark Rees on 2004-03-30 05:18:30
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (6)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2017 by Animus Pactum Consulting. All rights reserved. Privacy Information