There are 1000 light bulbs all switched off. Starting with number 1, going up to 1000 by jumps of one (i.e. 1, 2, 3, etc.), you will turn ON each light bulb that is off, and each light bulb that is on will be turned OFF, then you start again going up this time by jumps of two (i.e. 2, 4, 6, etc.) Start all over again with jumps of three (i.e. 3, 6, 9, etc.), then jumps of 4, 5, 6 etc. until you reach jumps of 1000. Here is the question: how many light bulbs will be left on by the time you reach jumps of 1000? Remember on each jump you will turn ON each light bulb that is off, and each light bulb that is on will be turned OFF.