Does Throwing a Brick Overboard Increase or Decrease Lake Water Levels?

[vette982]

A man is in a rowing boat floating on a lake, in the boat he has a brick. He throws the brick over the side of the boat so as it lands in the water. The brick sinks quickly. The question is, as a result of this does the water level in the lake go up or down?

Answer: http://mindcipher.com/puzzle/97-open-water"

 

[djeitnstine]

Of course the net result is the water level going down. Because the block in the boat displaces an amount of fluid equal to the block's weight. However when the block is thrown overboard, the resulting volume of displaced fluid is much less, therefore the level must be lower.