Find The Next Number in this series.
1, 2, 6, 42, 1806 ?

What's the only room from which no one can enter or leave

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?

Which is the rope you never skip with?

John is selling fruits.
He sells grapes at $30, Dates $25, and a Wolfberry $45.
At what price does he sell fig?

PS: Logical Thinking

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

Move four matchsticks to the below square to form three squares?

What part of the chicken has the most feathers?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?