I have teeth but i don't bite. Who Am I ?

I am white when I am dirty, and black when I am clean. What am I?

What can run but never walk, have a mouth that never speaks, have a head that never weeps, and have a bed but never sleeps?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

I don't get anymore wetter, no matter how much rain falls on me.

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?

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

What brings you down but never up?

What number comes next in the series?

5 15 5 18 5 24 14 20 _