If two's company, and three's a crowd, then whats four and five ?

Once upon a time, there was a castle on a square island. The entire island was surrounded by a 14m wide trench. The Romans had wanted to invade the castle and had brought a few wooden planks along with them to facilitate themselves in crossing the moat. The planks were however found to be only 13m long.

The Romans still managed to cross the trench. How did they do it?

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

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

If 1+9+8=1, what is 2+8+9?

A man is shown a portrait painting. He looks closely, then tells, “Brothers and sisters have I none, but that man’s father is my father’s son!” Who is the man in the portrait?

A woman lives in a Tall building thirty-six floors high and 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?

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?