An amoeba was placed in a test tube, and exactly an hour later the test tube was filled with amoeba.

An amoeba was placed in a test tube, and exactly an hour later the test tube was filled with amoeba. How long does it take for half of that tube to fill with amoebae if each amoeba divides by two after one minute?

Since each amoeba divides into two in one minute, then one minute before it is completely filled, there was one amoeba in the test tube instead of every two, that is, the test tube was half full. In an hour 60 minutes, then the tube will be half full in 60 – 1 = 59 minutes.
Answer: 59 minutes