What's the only room from which no one can enter or leave

Can you find out the remainder when 3^300 is divided by 5?

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

What does it mean?

There is a barrel with no lid and some wine in it. 'This barrel of wine is more than half full,' said Curly. 'No it's not,' says Mo. 'It's less than half full.' Without any measuring implements and without removing any wine from the barrel, how can they easily determine who is correct?

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?

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

why?

What's the best place to go shopping in the ocean?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

A man stands on one side of a river, his dog on the other. The man calls his dog, who immediately crosses the river without getting wet and without using a bridge or a boat. How did the dog do it?