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.

How many triangles can you count in the figure given?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

What numbers should go on the bottom line?
3 6 9 15
8 2 10 12
11 8 19 27
19 10 29 39
? ? ? ?

Snow and Tyrion are two mad logicians who love betting. They placed 11 Candies at the table and designed a small betting game, in which both of them needed to eat Candies turn by turn with the following rules:

Rule 1: One needs to eat at least one candy.
Rule 2: One cannot eat more than 5 candies.

The one that eats the last candy will lose. Snow won the toss and needs to start. How many candies must Snow earn to make sure that he wins the bet?

What number comes next in the series?

5 15 5 18 5 24 14 20 _

I have a big mouth and I am also quite loud! I am NOT a gossip but I do get involved with everyone's dirty business.

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

Use the digits from 1 up to 9 and make 100.

Follow the rules.
=> Each digit should be used only once.
=> You can only use addition.
=> For making a number, two single digits can be combined (for example, 4 and 2 can be combined to form 42 or 24)
=> A fraction can also be made by combining the two single digits (for example, 4 and 2 can be combined to form 4/2 or 2/4)

Question: how can we do this?

How can a man go eight days without sleep?