What is the fastest way to double your money?

4 fathers, 2 grand-fathers and 4 sons went to watch the movie.What is the minimum number of tickets they need to buy ?

Count the number of triangles in the given picture.

Can it be possible to build a house that has all its four walls facing towards the South?

Take away the whole and some still remain. What is it?

What kind of band never plays music?

All of Jacob's shoes are red except two.
All of Jacob's shoes are green except two.
All of Jacob's shoes are yellow except two.

How many shoes does Jacob have?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?