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

Solve the below puzzle by replacing the question mark with the correct number.

3 6 12

4 8 16

5 10 ?

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

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?

You have a roll of cloth 1km long. You have a machine which cuts this roll into pieces of 10-meter-long cloth.

How long would it take for the machine to cut the roll if each cut took 4 secs?

Using Only Five 5's and any mathematical operator make sum as 37

Once while in his court, King Akbar asked Birbal to write something on a wall that makes one sad when read in good times and makes one happy when read in sad times.

He took only a few moment and wrote something that fit the requirements. What did he write?

What is the last thing you take off before bed?

What can run but never walks, has a mouth but never talks, has a head but never weeps, has a bed but never sleeps?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?