Can you fill the blank with the correct number?

6 30 870 756030 _____

You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

I was speeding and ran through a stop sign, yet two traffic officers who were there do nothing about it.

why?

A woman lives in a skyscraper thirty-six floors high and is served by several elevators which stop at each floor going up and down. Each morning she leaves her apartment and goes to one of the elevators. Whichever one she takes is three times more likely to be going up than down. Why?

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?

The centre of the third figure is empty. What digit should fit inside?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Replace the question mark with the correct number in the below-given picture?

Decode below rebus
D
N
A
T
S , D