Day away - science puzzle
Sarah and Mike conclude that it is wednesday. But five minutes later it is already friday. How is that possible?
Boat and stone - science puzzle
Suppose you sit in a rubber boat in a swimming pool. In the boat lies a stone. You throw this stone from the boat into the pool. Will the water level in the pool raise or drop?
Brick tower - science puzzle
Suppose you have an infinite number of bricks and no cement or another material to connect the bricks to each other. You would like to build a tower like the one in the figure. How many bricks do you need in order to build a tower in which the highest brick is shifted three bricks with respect to the lowest brick?