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Perfect Eggs

Math brain teasers require computations to solve.

 

Puzzle ID:#1403
Fun:*** (2.6)
Difficulty:** (1.92)
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?

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Comments

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*en*
Jul 03, 2005

Like it
Very clever
thompson1Aus*
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!
xdbtcpAus*
Aug 04, 2014

Thought it was a trick question - you can't use timers to boil an egg
Guess I shoulda checked the category



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