Solution:

The number will be 30.

In the first circle
(5 + 4) * 2 = 18

In the third circle
2. (12 + 8) * 3 = 60

In the fourth circle
3. (3 + 9) * 4 = 48

Similarly In the fifth circle
4. (4 + 2) * 5 = 30

Solution:

None

The sum of numbers from 0-9(0,1,2,3,4,5,6,7,8,9) is 45 and therefore can be divisible by 3 and 9.

Solution:

Slumdog Millionare = Slum + Dog + Million + air

Solution:

The woman told him to take out one nut each from the rest of the wheels and use them.

Solution:

9

Explanation:
2 < 3 < 5
To find out the required number of candies, take one in place of the least number (i.e. take one mango candy) and then add all the greater numbers (i.e. three strawberry and five pineapple candies) to it.

Required number of balls = 1 + 3 + 5 = 9.

Solution:

This is more of a philosophical question than being a riddle or a puzzle. The action of Brian directly led to the result which is the death of Chris. Thus he murdered Chris. In a sense, Chris died due to the lack of water. It is the circumstances that ultimately led to his death.

Solution:

A cigar stuck in the wall

Solution:

Batsman hit six and gone retired hurt while the new batsman come to play and get runout for his wicket and the other batsman hit six and made both century and team win..

Solution:

In the picture you can find the green matchsticks. We have moved them from the bottom and placed them in the middle. It was a bit tricky but now you have your desired result.

Solution:

The stranger said that he thought the room was his. If so, he must have had the keys to the room and thus he must not have knocked.

Solution:

The attached picture shows you how you can do it. If you were able to deduce any other way, feel free to comment.