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


2 Comments on "Remote Cooking"

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

Leave a comment

First name (required)

Email (will not be published) (required)