The initial population of a town is 127,866 and it grows with a doubling time of 13 years. What will the population be in 23 years?

226,224.

If it takes 13 years to double the population of already 127,866, that means that it grows around 9836 people annually. 23-13 = 10, so multiply that by 9836, giving you 98,358 because thats the remaining years after the population doubles. So, 255,732, which is the doubled population after 13 years + 98,358, the population after the remaining 10 years = 354,090, the population after 23 years.