Hourglasses

You have a 7-minute hourglass and an 11-minute hourglass. How can you measure exactly 15 minutes with them?

Turn both hourglasses upside down. When the time of the 7-minute hourglass runs out, turn it upside down. When the time of the 11-minute hourglass runs out, turn the 7-minute hourglass upside down again. Finally, when the time of the 7-minute hourglass runs out, exactly 15 minutes will have been passed.

+ latest posts

We do not know where this puzzle originated from. If you have any information, please let us know via email.

Responses

Your email address will not be published. Required fields are marked *