A culture of a certain bacteria doubles every hour. At 9:00 am, there were already 120 bacteria.
To find out when the bacteria population will reach a certain number, we need to determine the growth rate per hour.
Let's calculate the growth rate by subtracting the initial population from the final population and dividing it by the time taken.
Final population = 120 bacteria * 2 = 240 bacteria
Time taken = 9:00 am to 10:00 am (1 hour)
Growth rate = (Final population - Initial population) / Time taken
Growth rate = (240 bacteria - 120 bacteria) / 1 hour
Growth rate = 120 bacteria/hour
Now that we know the growth rate, we can find out when the bacteria population will reach a certain number.
Let's say we want to know when there will be 1000 bacteria.
Time = (Final population - Initial population) / Growth rate
Time = (1000 bacteria - 120 bacteria) / 120 bacteria/hour
Time = 880 bacteria / 120 bacteria/hour
Time = 7.33 hours
Therefore, the bacteria population will reach 1000 bacteria at approximately 4:20 pm.