Brain Teasers Optical Illusions Puzzle Hunts Codes & Ciphers Mechanical Puzzles
Personal Links
Browse Teasers
Search Teasers

Hour Glass

Logic puzzles require you to think. You will have to be logical in your reasoning.


Puzzle ID:#29696
Fun:*** (2.93)
Difficulty:** (2.09)
Submitted By:npf2005*




With a 7-minute hourglass and an 11-minute hourglass, can you explain the quickest way to time a boiling egg for 15 minutes?


Start both hour glasses as the egg is dropped in the boiling water. When the sand stops running in the 7-minute hourglass, turn it over. When the sand stops running in the 11-minute hourglass, turn the 7-minute hourglass over and leave the 11-minute hourglass. When the sand stops in the 7-minute hourglass, 15 minutes will have elapsed.

What Next?


See another brain teaser just like this one...

Or, just get a random brain teaser

If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.


Back to Top

Online Now
4 users and 588 guests

Users In Chat
Follow Braingle!
Fold 'N Fly Paper Airplanes
Easy to follow folding instructions and videos.
Copyright © 1999-2017 | FAQ | Widgets | Links | Green | Subscribe | Contact | Privacy | Conditions | Advertise | Braingle Time: 7:26 pm
Sign In Create a free account