Why do we preferably have round manhole covers and not square ones?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

How is a fly different from a mosquito?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

A boy collects white seashells from the sea and brings them home every night. When he has enough of them, he decides to sell them to a trader.

The trader is ready to buy the shells and he asks the boy about the quantity. At this, the boy starts calculating. He has a giant box that contains 3 mini boxes. Two of them have another mini box inside. If the giant box can hold 50 shells, how many brown shells can he sell to the trader?

Replace the letters of words with a number so that the below equation holds true

BASE +
BALL
---------
GAMES
----------

What does below pictogram mean?

During which month do people sleep the least?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?