If you save $250 each year for the next 20 years, how much money would you have if you earned 9%?

Answer 1

This is called a "sinking fund"

S = N [ (1+r)^n -1 ]/r

N = amount deposited each period
r = decimal interest rate per period
n = number of periods, compounded

here
N = 250
r = .09
n = 20
so
S = 250 [ (1.09)^20 -1 ] / .09
S = $ 38,370.09