A Petri dish hosts a healthy colony of bacteria. Once a minute every bacterium divides into two. The colony was founded by a single cell at noon. At exactly 12:43 (43 minutes later) the Petri dish was half full.

At what time will the dish be full?

At what time will the dish be full?

Solution:

The dish will be full at 12:44.

Answer for old wording:

The saucer was half full at 11.59 - the next minute there will be twice as many of them there (so full at 12.00).