Can you find the key in the picture below?

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

which number am I?

Our product and our sum always give the same answer. Who are we?

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

A man had five children. He had $100 with him to give to his children. He decided to start with the youngest child and then give $2 more than each younger child to his next elder child.

For example, if he gives $x to the youngest child, he will give $(x+2) to the next one, $[(x+2) + 2] to the next one and so on.

Can you find out how much did the youngest one receive?

If,

20 % 5 = 24

21 % 7 = 33

42 % 6 = 67

Then;

66 % 6 = ?

I have eight fingers and two thumbs but I do not live. What Am I?

I shave every day, but my beard stays the same. What am I?

Why is a river so rich ?

An exterior architect is asked by a builder to plant seven trees in a manner that there are exactly six rows of trees in a straight line and each row has three trees in particular.

How will he do it?