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?
(In reply to Closer and closer
by Brian Smith)
Great! I like it -- much cleaner than the mess I was working with. But can anyone figure out how to do something like this and keep it to a finite amount of time? The problem seems to be that the small bits of the hour are always at the tail end of an hour's worth of clock doubling....