A killer told a detective that he would commit his next crime in the only place in Paris where you couldn’t see the Eiffel Tower. How did the detective end up catching him?
You turn the 7 minute one and the 11 minutes one at the same time. When the 7 one finishes, turn it again. When the 11 one finishes, you know that 4 minutes have passed, with 4 minutes to get to the desired 15, all you need to do now is turn the 7 minute hourglass again since it counted 4 minutes, and when it runs out it'll be exactly 15 minutes.
Google Riddle - The Coin Tower
Riddle:
If you pile up coins one on top of another until they get as high as the Empire State Building - would you be able to fit them all into one average sized room?
(The 'Google Riddles' are interview questions those who wish to get hired were asked).
Yes, you could.
How do we know this? If the Empire State Building is about 100 levels tall, and each level is about an average room in height, that means we can divide the giant pile into 100 piles of one level each. Would 100 piles of coins fit in a room? Of course it will, with lots of room for more.
Small But Mighty
Riddle:
I may be small, but I can climb a tower.
What am I?
Two sisters we are, one is dark and one is fair,
In twin towers dwelling we're quite the pair,
One from land and one from the sea,
Tell us truly, who are we?