Need help with exponential curve

Year 1950 1960 1970 1980 1990 2000

t 0 10 20 30 40 50

p(t) 69,000 119,594 207,287 359,282 622,726 1,079,342

I already have the average rate of growth from 1970 to 1980 is 15199.5: because p(30)-p(20)/30-20= 359,282-207,287/10=15199.5

I also have the average rate of growth on 1990 to 2000 as 45661.6.

My question is approximating the growth rate of the city in 2000. I tried putting the all the variable in my calculator and did the exponential curve. But, it wasn't right.

The answer for the instantaneous rate of growth is 60,115 (for 2000). I need to know how to get that answer!