I am doing an IRR internal rate of return example and I understand all of it but the part where you divide the investment by the annuity and get the approximation. after i get say the # 2.353 then I go to the appendix D for the value of n which is 3 , the solution says the percentage is between 13 and 14 %.

My question is how did they get this estimation or approximation it does not make since to me can you clarify for me please?