I’m tall when I’m young, and I’m short when I’m old. What am I?

Name a key which is hardest to turn.

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

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

John can eat 27 chocolates in an hour, Jacob can eat 2 chocolates in 10 minutes, and Jolly can eat 7 chocolates in 20 minutes. How long will it take them to share and eat a box of 120 chocolates whilst playing Chess?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

What number when divided in half becomes zero?

Identify Me

Hint1: I am a god
Hint 2: I am a planet
Hint 3: measurer of heat

A train leaves from point A for point B at 80 mph. After half an hour, another train leaves from point B for point A at 60 mph.

Which of the trains will be farther from point A when they meet ?

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.