It will take 10 years for harikiran to pay off Rs. 10000 in 10 yearly

installments.

∵ He pays 10% annual interest on interest on remaining amount

∴ Money given in first year

= 1000 +  $\frac{10000\times 10}{100}$ = Rs. 2000

Money given in second year = 1000 + interest of (10000 - 1000) with interest rate 10% per annum

= 1000 +  $\frac{9000\times 10}{100}$ = Rs. 1900

Money paid  in 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

=  $\frac{10}{2}$[2(2000) + (10 - 1)(-100)] = Rs. 15500

Therefore, total money given by harikiran 

= 5000 + 15500 = Rs. 20500.