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?

You can hear me, but you can't touch or see me.

What am I?

81 x 9 = 801. What must you do to make the this equation true?

No matter how little or how much you use me, you change me every month. What am I?

I speak without a mouth, and hear without ears. I have no-body, but I come alive with the wind. What am I?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

Krish is 45 years old and his mother Crishtina is 73 years old.

Can you find out how many years ago, his mother was three times his age?

On a special event at the prison, 5 prisoners John, Jacob, Krist, Tang, and Dang given a chance to go to a sauna and can bring one thing with them.

Following are the things that the prisoners bring with them.
John: A soda
Jacob: Thermos
Krist: Book named "How to kill"
Tang: A Walkman
Dang: Harmonica

Since it is a Sauna, no one can see each other. After a while When the steam is switched, Tang was found dead and there was blood all around.
J Bond was called and he instantly come to know who can be the murderer. How?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

Can you find out the remainder when 3^300 is divided by 5?