What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Who always enjoys poor health?

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 miles long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 mph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

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

I can write cow in 13 letters.

Can You?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

What two things can you never eat for breakfast?

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.

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?