Eight of us go fourth, not back, to protect our king from an attack. What are we?

Can you find a five letter word that is left with only two letters if one is removed?

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle:

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

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

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

You can hear me, but you can't touch or see me.

What am I?

It belongs to you, but other people use it more than you do. What is it?

You are given 16 witch hats. The hats are divided in four different colours – red, blue, green and yellow. Every colour has been assigned to four hats. Now each of the hat will be glued with a label of an arithmetic sign – ‘+’, ‘-‘, ‘x’ or ‘/’. But you can label one sign only once on one colour. In such an arrangement, the hats can be uniquely defined by its colour and symbol.

Can you arrange all the 16 hats in a 4x4 grid in a fashion that no two rows and columns have a repetition of colour or sign?
We have arranged four hats in the below picture to assist you.

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?