What is the next number in this matchsticks series riddle?

When it's bad luck to meet a black cat?

There was an aeroplane crash, every single person died, but two people survived. How is this possible?

I have a big mouth and I am also quite loud! I am NOT a gossip but I do get involved with everyone's dirty business.

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.

A man was just doing his job when his suit was torn. Why did he die three minutes later?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

What happened when the wheel was invented?

In a school, 280 students studied chemistry, 254 students studied physics and 280 students studied biology.

97 students studied chemistry as well as physics, 138 students studied physics as well as biology and 152 students studied chemistry as well as biology.

73 students studied all the three branches.

Can you find out the total number of students?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?