A mathematician, a physicist and an engineer were each given the following problem to solve.

A school dance floor included a straight line down the middle dividing the floor in two equal halves. Boys were lined up against one wall and girls against the opposite wall, each facing the centre line. They were instructed to advance in stages towards the centre line every ten seconds, where the distance from the person to the centre line at each stage is equal to one-half the distance at the past stage.

i.e.: If the starting distance from the wall to centre line was D, the progressive series of distances at t = 0, 10 seconds, 20 seconds...10n seconds to the centre line is (D, D/2, D/4, D/8, .....D/2n)

The question is, when will they meet at the middle?

The mathematician said that they would never meet.

The physicist said they would meet when time equals infinity.

The engineer said that in one minute they would be close enough for all practical purposes.