How many bananas can you eat if your stomach is empty?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

John said, "If yesterday was tomorrow, today would be Friday."

When did John make this statement?

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

There are a hundred statements.

First person says: At least one of the statements is false.

Second person says: At least two of the statements is false.

Third person says: At least three of the statements are false.

Fourth person says: At least four of the statements are false.

..

..

..

Hundredth person says: At least a hundred of the statements are false.

Analysing it, how many statements do you think are false and how many are true?

What is next number in the pattern below:

131 517 192 123 ?

Which tank will fill first?