Why do people go to bed?

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.

You are playing a game with your friend Jack. There are digits from 1 to 9. You both will take turn erasing one digit and adding it to your score. The first one to score 15 points will win the game.

Would you want to play first or second?

PS: The sum should be exactly 15.

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

There are two dice with empty faces in front of you and a marker. You can mark any number on each of the faces of the two dice, but you have to display all 31 days of the month using the two of them.

Which numbers will you mark on which dice so that you can easily depict all the dates of the month?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

What is the word or phrase?

Can you find a number that lies one third of the distance between 1/3 and 2/3?

Can you guess the name of the month by looking the below rebus ?