81 x 9 = 801. What must you do to make the this equation true?

A father's child, a mother's child, yet no one's son.

Who am I?

Replace the question mark with the correct number below.

Can you tell a 3D object that has just two surfaces?

What is the fastest way to double your money?

The King of a distant land had heard that Birbal was one of the wisest men in the East and so desired to meet Birbal. He sent Birbal an invitation to visit his country.

In due course, Birbal arrived in the distant kingdom. When he entered the palace he was flabbergasted to find not one but six kings seated there. All looked alike. All were dressed in kingly robes. Who was the real king?

The very next moment he got his answer. Confidently, he approached the king and bowed to him.

How did Birbal know who was the real king?

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

Can you replace the question mark with the correct number?

You are provided with a grid (as shown in the picture). Can you fill the squares with numbers 1-8 in a manner that none of the two consecutive numbers are placed next to each other in any direction (vertically, horizontally or diagonally?)

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.