What is the fastest way to double your money?

I’m orange, I wear a green hat and I sound like a parrot. What am I?

What is the centre of gravity?

The more of this there is, the less you see. What is it?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

Which is faster, Heat or Cold ? Explain.

Why is the Hole below a Lock?

Can you solve the rebus below?

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?