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

In the Chess Board picture below white army is arranged. You need to add a black army on the board such that no piece is under any threat.
Note: Army comprised of 1 king, 1 queen, 2 rooks, 2 bishops, 2 knights, and 8 pawns.

The centre of the third figure is empty. What digit should fit inside?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

Rahul decided to meet Simran so he boards a local train from Bombay station. Just after the station, there is a 1km long tunnel. The train starts and is now accelerating. Rahul is a claustrophobic guy, so what is the best position for him to sit?

A Shopkeeper sold a few chickens to four different customers on a particular day. It was such that each customer purchased half of the remaining chickens and half the chicken more.

Can you find out how many chicken were sold by the shopkeeper on that day if we tell you that the fourth customer bought a single chicken ?

How many times do a clock's hands overlap in a day ?

What does this rebus means ?

PROG WORKRESS

Bay of Bengal is in which state?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?