When exposed to sunlight, the number of bacteria in a culture decreases exponentially at the rate of 10% per hour. What is the best approximation for the number of hours required for the initial bacteria to decrease by 50%?

A culture of 3,000 bacteria triples every 40 minutes. If P(t) represents the size of the bacteria population after t minutes, which equation can be used to model the exponential growth of these bacteria?

A radioactive substance has an initial mass of 250 grams, and its mass halves every 5 years. Which equation shows the number of grams, M(t), remaining after t years?

A scientist studying bacteria growth notices interesting behavior with the replication of cells over the course of 24 hours. She records her description of the behavior in hopes of writing a function that can be used to make predictions for future bacteria growth. She observed that for the first 8 hours, the number of bacteria, y, increases at a constant rate of 10 cells per minute. After the initial 8 hours, the number of bacteria varies inversely with time, x, with a proportional constant of 3 for the next 10 hours. Between hour 18 through hour 20, the bacteria decrease at a constant rate of 5 cells per minute. In the last 4 hours, the bacteria double in growth every minute. Which of the following models best fits the scientist’s observations?