Mind Bender # 11 : Hour Glass Figures

Posted on 10. Oct, 2007 by in Mind Benders

Hour GlassYou 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?