A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

While going to your grandmother's house, you counted Twenty houses on the right side. While returning back to your home, you counted Twenty houses on the left side.

How many houses are there between your home and your grandmother's home?

How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started?

Can you find out the remainder when 3^300 is divided by 5?

A bomb exploded in a room full of married couples and no one died. How?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

When monkey rotate the gear, which mark will be hit 1 or 2 ?

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

What am I?