Video explains how to solve the following brain teaser: One hundred light bulbs are arranged in a row. Each light bulb can be either on or off. On the first pass of the row, each bulb is switched on. On the second pass, every other bulb is switched to off. On the third pass, every third bulb is switched. This process continues for a hundred passes. The question is: After one hundred passes, how many light bulbs are switched on? [11:19]