Why do people go to bed?

Which number should replace the question mark?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

John was piloting a plane behind a car but was never able to overtake it. Why?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

Which word does the below Plexor means ?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

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