Mind Bender # 11 : Hour Glass Figures
Posted on 10. Oct, 2007 by Chris Lang in Mind Benders
You have just discovered your watch has broken, and that you only have two Hour Glasses in the house ...
> one to measure 4 minutes; and
> another to measure 7 minutes.
Your dilemma is that you need to time something for 9 minutes!
How do you go about doing that?





