What does below pictogram mean?

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?

What always comes into a house through the keyhole?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

Solve this riddle by finding the odd one out from the rest.

Why is a river so rich ?

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

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

Prove that twice of ten is the same as twice of eleven.

In The 1st month of this year(the year 2013), I noticed that the date 13-1-13 (13 January 2013) is special.

This date is special as:

Date * Month = Year.

Can you figure out which year of this century has a maximum number of such dates?