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?
Does this mean that a clock's speed can be doubled ad nauseam  i.e. taking the original clock  pressing double speed twice implies that beep will go off in 15 mins? 3 presses and 7.5 minutes?

Posted by TJ
on 20031013 19:09:20 