If your bacteria reproduce every 20 minutes how many bacteria would you have at the end of four hours assuming that you begin with one bacterium?

If bacteria reproduce every 20 minutes, this means they double in number every 20 minutes. After 4 hours (which is 240 minutes), there would be 12 reproduction cycles (240 minutes divided by 20 minutes). Starting with 1 bacterium, after 12 cycles, you would have 2^12 bacteria, which equals 4096 bacteria at the end of four hours.