If it took eight men ten hours to build a wall, how long would it take four men to build it?

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

What number do you get when you multiply all of the numbers on a telephone's number pad?

A word I know has six letters it contains, remove one letter and 12 remain. What is it?

Why is it against the law for a man living in Delhi to be buried in Mumbai?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

What does this rebus picture identify?

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?

There is a square piece of paper with a hole that is denoted by the circle on the top right side in the given picture. You have to cut the paper in a manner that it forms two and only two separate pieces of paper and then rearrange the pieces in a manner that the holes come in the centre of the paper.

John, Jack and Jill are in a desert. John doesn't like Jill and hence decides to murder him. He poisons the water supply of Jill. Since it is a desert area, Jill must drink or he will die of thirst.

Jack does not know of the actions of John and also decides to murder Jill. To succeed in his ill motives, he removes the water supply of Jill so he dies of thirst.

Jill dies due to thirst. Who murdered Jill?