Can you replace the question mark with the correct number?

What month of the year has 28 days?

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?

Yesterday I fell from 30 feet high ladder but I don't get hurt. Why?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

In an Art Gallary, When the clock hit 11 am, Artist hung the painting number 30. When it struck 4 pm, he hung painting number 240 and when it struck 7:30 pm, he hung painting number 315.

Can you determine, which painting number will he hang when the time is 9:20 pm?

Two-person want to cross a river. Only one boat is present on the riverside that can carry only one person at a time.

However, they still manage to cross the river. How is it possible?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

This is a simple one. You just have to count the number of Fs in the given sentence.

Finished Files are the result of years of scientific study combined with the experience of years.

How many did you count?

A four-digit number (not beginning with 0) can be represented by ABCD. There is one number such that ABCD=A^B*C^D, where A^B means A raised to the B power. Can you find it?