If bacteria divide every 30 min, and you start with a single bacterium at noon, how many bacteria will you have just after 2:00 pm?

You'd start with 1 at 12:00

Then at 12:30 that would divide into 2

At 1:00 those 2 would divide into 2 more and you'd have 4

At 1:30 the four would divide into 2 as well, giving you 8

At 2:00 The 8 would divide into 2 once again, and you'd have (end) with 16