Final answer:
The bacteria population will be 6000 after 40 minutes.
Step-by-step explanation:
To find the size of the bacterial population after 40 minutes, we need to determine how many times the population doubles in that time period. Since the bacteria double every half hour, in 40 minutes (which is equivalent to 2/3 of an hour), the population will double twice. So, the size of the bacterial population after 40 minutes is 1500 x 2 x 2 = 6000 bacteria.