Why do we preferably have round manhole covers and not square ones?

How can you drop a raw egg from a height onto a concrete floor without cracking it?

Given that

(78)^9 = 6
And (69)^4 = 11

Can you find out

(99)^2 =?

(Note: This is Logical, not Mathematical)

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

A detective visits his friend John just to discover that John's neighbour Dr Jacob was murdered. Dr Jacob, who is a mathematician wrote the murderer's name in a code word "Hcqtfz". There were five suspects
1. Ajit
2. Pankaj
3. Ganpat
4. Deenu
5. Hariya

The Detective was instantly able to find the murderer.
Can you?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?

What is the below Rebus indicate?

How can you write nineteen in a manner that if we take out one, it becomes twenty?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.