in my book, they gave formula: y = y1e^kt (y1 base amount).

the problem is: "The population of the US was 3.9 million in 1790 and 178 million in 1960. If the rate of growth is assumed proportion to the number present, what estimate would you give for the population in 2000?"

i got 3,900,000^(170k) = 178,000,000 to try to solve for the rate but i dont think thats right.

the other one is: A population is growing at a rate proportion to its size. After 5 years, the population size was 164,000. After 12 years, the population size was 235,000. What was the original population?

i tried to set up the base amount with an x and try different approaches but it didn't work. please help.