How many times in a given day, minutes and hour clock comes in a straight line ?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

Who is that with a neck and no head, two arms and no hands? What is it?

What has one eye, but can’t see?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

John was driving a bus and got stuck when passing through an underpass. Then came Jacob with a needle and got the bus out of the underpass.

What did the boy do?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

There are forty elephants and they have forty-fore heads. How can this be possible?

Andrew’s doctor gives him three pills and tells him to take one every half hour. How much time will have passed by the time Andrew’s taken all three pills?