I started the year with a known amount of funds in my account and I make regular (assume equal) monthly payments into the account.
I know how much my gain/interest for the year is. I believe the interest is calculated monthly, so there's compound interest from the monthly payments.
I know how I would calculate it if there were no monthly payments, but not with the included. How can I calculate the equivalent annual interest rate in this situation?
If you'd like some rough numbers:
Start balance: 1000
Average monthly contributions: 100
Interest paid end of year: 90