Brain Teaser

[pokerfan]

Your rich uncle dies, and you’re in his will. From his vast collection of timepieces, he leaves you the 7-minute hourglass and the 11-minute glass. To honor his memory, you open a reflexology salon and use the hourglasses when you give foot massages. But your clients want 15-minute massages. How do you use your timepieces and still manage to please your clients?

[tkmorris]

1. Easy

Start both glasses. When the 7 minute runs out, immediately flip it and allow it to start again. When the 11 minute one runs dry, the 7 minute one has precisely 4 minutes of sand in the bottom. Flip it over, and allow it to finish.

Voila, 15 minutes.

[pokerfan]

3. Yeah, I thought it was pretty trivial by Ask Marilyn standards

That's the answer I got.

[krispos42]

7. Good one

I was stumbling on the last part. I had this idea of lying the 11-minute one on it's side to hold those 4 minutes in reserve, but couldn't figure out how to integrate it into a workable solution!

[democracyindanger]

2. I think I got it

Start both the 7 and 11 minute glasses at the same time. When the 7 minute glass runs out, start the massage, which leaves you 4 minutes on the 11 minute glass. Turn the 11 over once more and you'll get 15 minutes.

[pokerfan]

4. What if you don't want to wait 7 minutes

before starting? tk's solution allows for a massage to begin immediately and the hourglasses ready for another one immediately after.

[democracyindanger]

5. Yes, but my solution

allows for 7 minutes of new age music to play softly in the background before beginning the massage, increasing the chance of a good tip.

:P

[pokerfan]

6. Which is a good thing

Since you're only running at 68% of capacity you're gonna need those tips. :P