I travel all around the world but always stay in the corner. What am I?

What occurs twice in a week, once in a year but never in a day?

Can you make a fire with just a single stick?

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

All of Jacob's shoes are red except two.
All of Jacob's shoes are green except two.
All of Jacob's shoes are yellow except two.

How many shoes does Jacob have?

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

How many times can you subtract the number 5 from 25?

I look at you, you look at me, I raise my right, you raise your left. What am I?

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 brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?