# Financial Math - Compound Interest Rate

I have PV, PMT and N. I want get I (Tax).

Please, if I'm not clear, help me adjust this Question. I don't know nothing about Financial Math. I'm programmer, I need get something like TIR function of Excel and recreate in Python. I just want the instruction.

Example

PV = 1.000
PMT = 80
N = 24
I = ????


The expected value of I is: 8.6%

• The English name for TIR is IRR. But this seems to be a question about Excel, not mathematics. – Michael Greinecker Oct 3 '17 at 19:31
• I is not tax, it is the interest rate! – alexjo Oct 3 '17 at 19:32
• Yes, interest rate. compound interest rate – Guilherme IA Oct 3 '17 at 19:37