1: A bacterium divides four times an hour, and each time it becomes twice as big as the previous one, so a bacterium becomes1* 2 * 2 * 2 =16 after one hour, so 100 bacteria is100 */.

At 2: 3 hours, the bacteria divide 12 times, and once it becomes1* 2 * 2 * 2 * 2 = 4096, so 100 is 4096 * 100.