What's the only room from which no one can enter or leave

What can go up a chimney down, but can’t go down a chimney up?

The doctor advised his patient to take a tablet after every fifteen minutes. He gave him five tablets in total.

How much time will he take to have all the five tablets?

I am sure no one can have two things for dinner. what are they?

A man has to get a fox, a chicken, and a sack of corn across a river.

He has a rowboat, and it can only carry him and one other thing.
If the fox and the chicken are left together, the fox will eat the chicken.
If the chicken and the corn are left together, the chicken will eat the corn.

How does the man do it?

Why is a river so rich ?

I always drive my customer away.

Who am I?

A clock loses 10 minutes each hour. If the clock is set correctly at noon, what time is it when it reads 3 PM?

Count the number of balls in picture below:

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?