Final answer:
The population of the town can be found using the differential equation dt/dy = ky with a growth constant k = 0.07 year^-1. To find the population at the start of the year 20, we use the formula P = P0e^kt and substitute t = 20.
Step-by-step explanation:
The population of a town is growing according to the differential equation dt/dy = ky, where k is the growth constant. In this case, k is equal to 0.07 year-1. To find the size of the population at the start of the year 20, we can solve the differential equation.
The solution to the differential equation is given by the formula P = P0ekt, where P0 is the initial population size, k is the growth constant, and t is the time.
Since we want to find the population at the start of the year 20, we substitute t = 20 and solve for P.