If eleven plus two equals one, what does nine plus five equal?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

Find out which of the given views in the picture is accurately the top view of the given pyramid.

Why do you find that most of the buildings are deprived of the 13th floor?

Can you fill the blank with the correct number?

6 30 870 756030 _____

How many bricks does it take to complete a building that is 15 feet wide, 30 feet deep, and 12 feet tall made of brick?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

'S' refers to the number of seconds in a day and 'H' refers to the number of hours in ten years. Which quantity out of these two is greater?

One day Jenifer meets the Lion and the Tiger in the Forest of Forgetfulness. She knows that the Lion lies on Mondays, Tuesdays, and Wednesdays, and tells the truth on the other days of the week. The Tiger, on the other hand, lies on Thursdays, Fridays, and Saturdays, but tells the truth on the other days of the week. Now they make the following statements to Jenifer:

Lion: Yesterday was one of my lying days.

Tiger: Yesterday was one of my lying days too.

What day is it?