Two sand glasses – Brain Teaser

9 Comments

1. Mr. W says:

   June 5, 2009 at 5:52 pm

   Tell your cook to do it

   Reply
2. Muhammad says:

   June 3, 2009 at 5:27 am

   At Time=0
   Start both 4 & 7 Timer
   At Time= 4
   Restart The (4 min.) Timer
   At Time = 7
   Restart The (7 Min.) Timer
   ** Begin The Cooking
   At Time = 8
   (When The 7 Min. timer run out)
   restart the 4 min. timer
   At time= 12
   restart the 4 min. timer

   So : the cooking time = 1 + 4+ 4 = 9 min.

   Reply
3. admin says:

   May 29, 2009 at 12:35 am

   Good job everyone,
   Here is my solution. It is fairly similar to some of yours.
   Start both timers simultaneously, then turn the 4 minute one over as soon as it runs out. Then when the 7 minute timer runs out, turn it over. When the 4 minute timer runs out for the second time, turn over the 7 minute timer which has been running for 1 minute, and when it runs out, hey presto 9 minutes have elapsed.
   Thanks.
   Ken.

   Reply