In an experiment it is found that a culture of bacteria triples in number every four hours.
There are 200 bacteria at the start of the experiment.

Hours. 0, 4, 8, 12, ,16
No. of bacteria 200, 600, a, 5400, 16200

1. Find the value of a.
2. Calculate how many bacteria there will be after one day.
3.Find how long it will take for there to be two million bacteria.