what must the interest rate be if an investment is to double its value in 15 years, compounded monthly

in decimal form, rounded to 3 significant figures

2 answers

let the monthly rate be i
(1+i)^180 = 2
1 + i = 2^(1/180) = 1.003858..
so the monthly rate is .3858%
giving us a rate of
4.623 % per annum, compounded monthly
You have $1000 to invest. You place it in a money market fund that pays 8% compounded quarterly. How much will you have in the account at the end on 19 years?