## Remote Cooking

You are a cook in a remote area with no clocks or other way of keeping time other than a four-minute and a seven-minute hourglass. On the stove is a pot of boiling water. Jill asks you to cook a nine-minute egg in exactly 9 minutes, and you know she is a perfectionist and can tell if you under cook or overcook the egg by even a few seconds. How can you cook the egg for exactly 9 minutes?

1. Flip both hourglasses over and drop the egg into the water.
2. When the 4-minute timer runs out, flip it over (4 minutes elapsed, 3 remaining on the 7-minute timer).
3. When the 7-minute timer runs out, flip it over. (7 minutes elapsed, 1 remaining in the 4-minute timer)
4. When the 4-minute timer runs out, flip the 7-minute timer over. (8 minutes elapsed. 6 minutes remained in the 7-minute timer, but flipping it over leaves one minute’s worth of sand on top. When it runs out exactly nine minutes will have elapsed.)

Posted in Brain Teasers

Rusty says
December 17, 2015 @ 13:11

flip over 7 minutes hourglass and simultaneously flip over 4 minute glass. at the end of the 4 minute glass, there will be 3 minutes remaining in 7 minute glass.

flip over 3 minute glass simultaneously with 4 minute glass. When 3 minute glass id one, there will be one minute left in 4 minute glass.

you now have one minute to spare. flip over and use the one minute then flip over twice to get remaining 8 minutes.

Hannah says
June 18, 2018 @ 07:17

Tell Jill to make her own egg if she is gonna be so picky like that