Final answer:
The petri dish will go from half full to entirely full in 90 minutes, as that is the time it takes for the bacteria colony to double in size.
Step-by-step explanation:
The question revolves around the concept of exponential growth, which is an important concept in both mathematics and biology, particularly when studying populations of organisms like bacteria. If a colony of bacteria is expected to double every hour and a half (90 minutes), the amount of time it takes for the petri dish to go from half full to completely full is the same as the doubling time of the bacteria. As such, if the dish is half full, it will take exactly one more doubling period to become completely full. Therefore, the answer is 90 minutes, or 1.5 hours.