What is the coolest letter in the alphabet?

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

An evil man kidnapped someone and made them take one of two pills. One was harmless, but the other was poisonous. Whichever pill the victim took, the kidnapper took the other one. The victim took their pill with water and died. The kidnapper survived. How did the kidnapper get the harmless pill?

10+10 and 11+11 can give you the same answer.

Explain how?

This is a picture puzzle. You have to guess the name of the movie that can be related to the picture.

John is a strange liar.

He lies on six days of the week, but on the seventh day, he always tells the truth.

He made the following statements on three successive days:

Day 1: "I lie on Monday and Tuesday."
Day 2: "Today, it"s Thursday, Saturday, or Sunday."
Day 3: "I lie on Wednesday and Friday."

On which day does John tell the truth?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

How many triangles can you count in the figure given?

No matter how little or how much you use me, you change me every month. What am I?

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?