How to compute compounded interest rate?

I have the following scenario where i invest variable开发者_如何转开发 amount of principal every month,

Investment Month
$300       Jan
$200       Feb
$100       Mar

and i get a return of,

Returns    Month
$1000      Apr

How do i calculate the nominal annual interest rate if the amount is compounded monthly?

300*(1 + p/12)^(3) + 200*(1 + p/12)^(2) + 100*(1 + p/12)^(1) == 1000

Use bisection or something else to solve numericaly.

p=286%

EDIT: Best way to solve this numericaly is to apply Newton–Raphson method, since this equation can be simply derivated analytically.