What is so fragile that saying its name breaks it?

When I asked a girl's name she told me her name is the date '07/09/2001'.

I thought for a few seconds and then I got her name. Do you?

A girl rode into a tourist spot out of the city on Thursday. She loved the place and decided to stay for a few days. She stayed for four days and then she left for back home on Thursday.

How can this be possible?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

I’m tall when I’m young, and I’m short when I’m old. What am I?

Can you make the number 24 by utilizing the numbers 1, 3, 4 and 6? You must use one number only one time and you can use mathematical operation symbols anytime anywhere.

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

Forwards I am heavy, backward I am not. 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?