Prove that twice of ten is the same as twice of eleven.

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

There are forty elephants and they have forty-fore heads. How can this be possible?

If we change the South-East direction into North and North-East into West and all others similarly.
Can you find out which direction will be in the place of South-West direction?

Spot the cat in the picture below

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?

It is a six-letter word.
The first four letters are me.
The second and last letters are the same.
The fourth second and last letter is payment.

Who is it?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

You have to put a letter on the following to make it a meaningful word. The only challenge is that you can't use 'E'.

S E Q U E N C _