Puzzle: Two Hour Glasses

You have two hourglasses: a 7 minute one and an 11 minute one. Using just these hourglasses, how can you accurately measure time 15 minutes?

 

Hour Glass

 

Answer :

1.Start both the 7 minute hour glass & 11 minute hour glass.

2. Wait till the 7 minute hour glass times out. Time is 7 minute!

3. Restart the 7 minute hour glass. At this time 11 minute hour glass will have 4 minutes left to time out.

4. As soon as 11 minute glass times out invert the 7 minute hour glass. Total time now is 11 minutes.

5. After inverting 7 minute hour glass, it will now have 4 minutes left for time out.

6. After these 4 minutes times out, the total time is 15 minutes.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s