Can you find the missing piece of the Porsche?

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

Manish has to secure 40% marks to pass his B.tech final exams.
He got just 40 marks and failed by 40-marks.

What is the maximum marks?

I am white when I am dirty, and black when I am clean. What am I?

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?

If a wheel has 54 spokes, how many spaces are there between the spokes?

Count The number of F's in the paragraph below:

"FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS"

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

A new Engineering building containing 100 offices had just been completed. John was hired to paint the numbers 1 to 100 on the doors. How many times will John have to paint the number nine (9)?

You knock a Table over in the library, and suddenly 20 eyes are looking at you.