Weird Quiz

Que : You have two hourglasses--a 4-minute glass and a 7-minute glass.


You want to measure 9 minutes. How do you do it?

Ans : Start both hourglasses. When the 4-minute glass runs out, turn it
over (4 minutes elapsed). When the 7-minute glass runs out, turn
it over (7 minutes elapsed). When the 4-minute glass runs out this
time (8 minutes elapsed), the 7-minute glass has been running for
1 minute. Turn it over once again. When it stops, 9 minutes have
elapsed.