Harikiran purchased a house for Rs. 15000 and paid Rs. 5000 at once. Rest money he promised to pay in annual installments of Rs. 1000 with 10% per annum interest. How much money is to be paid by him in total?
Rs. 20500
It will take 10 years for Harikiran to pay off Rs. 10000 in 10 yearly installments.
∵ He pays 10% annual interest on interest on the remaining amount
∴ Money given at the end of first year
= 1000 + 10000×10100 = Rs. 2000
Money given at the end of second year = 1000 + interest of (10000 - 1000) with interest rate 10% per annum
= 1000 + 9000×10100 = Rs. 1900
Money paid at the end third year = Rs. 1800 etc.
So money given by Jairam in 10 years will be Rs. 2000, Rs.1900, Rs. 1800, Rs. 1700,......,
which is in arithmetic progression,
whose first term a = 2000 and d = -100
Total money given in 10 years = sum of 10 terms of arithmetic progression
=102[2(2000)+(10−1)(−100)]=Rs.15500
Therefore, total money given by Harikiran
= 5000 + 15500 = Rs. 20500.