When my father was 31 I was 8. Now he is twice as old as me. How old am I?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

Do You See It?

Seven Robbers robbed a bank and hide the coins in a lonely place.
They decide to divide the money equally the next morning. Two greedy robbers decided to cheat the others and reach the place at night. They equally divided the coins between them, one coin left. So they called another robber and then they decided to divide equally among the three. Sadly again one coin left. The same thing happened to the 4th 5th and the 6th robber.
However, when the 7th robber reached in the morning, they can divide the coins equally.

How many coins were there in total?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

John was piloting a plane behind a car but was never able to overtake it. Why?

How many times can you subtract the number two from the number fifty?

I don't get anymore wetter, no matter how much rain falls on me.

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

Why 1729 is a magic number? Answer Logically.