Sinking fund is the reciprocal of the final value coefficient of annuity, which refers to the problem of how much you can get by investing a sum of money every year for several years. Then, the question of reciprocity is how much you should invest to get a sum of money at the end of each year. How to distinguish it depends on whether he wants a sum of money at the end of each year. Annual capital recovery = the reciprocal of the present value coefficient of annuity, which refers to the investment of a sum of money at the end of each year. And how much money you should save now to invest every year. Then, the equivalent question is, how much money do you have now and how much money you have to recover every year to return it. How to distinguish it depends on whether he has money now.