Cook the cookie
We put the two hourglasses in one go, and when the 5 minute is over, it will be 8, 3 minutes left. At that moment we go around in 5 minutes.
When we finished 8, totally (it took us a total of 8 minutes), in 5 we got 2 minutes to finish.
At that very moment we turn around in 5 which will take 3 minutes to finish, which added to the 8 that had passed, will add 11 minutes in total.
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