Imagine you have invested $500 in an account that pays 5% simple interest per year. Can you find an arithmetic sequence to look for the amount of money in the account after 20 years?
since it is simple interest, the annual increase in the account would be .05(500) or $25
so in an A.S.
a = 500
d = 25
n = 20
term(20) = a+19d = 500 + 19(25) = 975