Why is it very easy to weigh a fish?

What has a bottom at the top?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

Can you decipher these quotes by Albert Einstein?
Blf xzm mvevi hloev z kilyovn lm gsv ovevo lm dsrxs rg dzh xivzgvw.

A man is lying dead in a field where no one is around. His head is split open and his legs are disfigured. Near to him, there is an unopened package. No living organism can be found anywhere at the crime scene.

How did he die?

Which is the smallest number that you can write using all the vowels exactly once?

Can you identify the direction in which this bus is moving; left or right?

Hint: The bus is moving on the roads of London.

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?

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

How do you go from 98 to 720 using just one letter?