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## Perfect Eggs

Math brain teasers require computations to solve.

 Puzzle ID: #1403 Fun: (2.59) Difficulty: (1.93) Category: Math Submitted By: gokaran

For his breakfast, Mr Stone likes an egg that has been boiled for exactly 9 minutes. He has two egg timers (those with sand in them), one that runs for 4 minutes and one that runs for 7 minutes. How can he use these timers to boil his egg?

Start both egg timers. When the 4 minute timer runs out, turn it over. When the 7 minute timer runs out turn it over. When the 4 minute timer runs out again the 7 minute timer has been running for 1 minute. Turn it over once again. When it stops the egg is done.
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 gakuka Mar 18, 2002 really clever! Of course, there are other ways, but yours was the easiest! captbob61 Mar 26, 2002 this may be easier... Let about half the sand run out of the 4. Then lay it on it's side, so that both piles in each end are the same height. Then put in the egg, run the 7, and THEN run the 4. dutchymonster Jul 03, 2005 Like it Very clever thompson1 May 25, 2006 I got to turn them both over at the same time (without starting the egg). Then turn over the 4 min. as soon as it finishes. When the 7 min. runs out, put the egg in (the 4 has 1 min left). Turn over the 4 when it ends. When 4 ends again, turn it over. When it ends again, the egg is done! xdbtcp Aug 04, 2014 Thought it was a trick question - you can't use timers to boil an egg Guess I shoulda checked the category