History of Hindu Mathematics: A Source Book v1.c8.s13.78

v1.c8.s13.78

(13) "A certain man borrows a certain (unknown) sum of money at an interest of 5 per cent per month. He pays the debt in instalments, due every ⅗ of a month. The instalments begin with 7 and increase in arithmetical progression, with 7 as the common-difference. 60 is the maximum amount of instalment. He gives in the discharge of his debt the sum of a series in arithmetical progression consisting of 60/7 terms. After the payment of each instalment, interest is charged only on that part of the principal which remains to be paid. What is the total payment corresponding to the sum of the series, what is the interest (which he paid), what is the time of the discharge of the debt, (and what is the principal sum borrowed)?"³