A man borrowed a certain sum of money at the rate of 6% per annum for the first two years, 9% per annum for the next three years, and 14% per annum for the period beyond 5 years. If he pays a total interest of Tk. 20900 at the end of 9 years, find the amount he borrowed.

Question: A man borrowed a certain sum of money at the rate of 6% per annum for the first two years, 9% per annum for the next three years, and 14% per annum for the period beyond 5 years. If he pays a total interest of Tk. 20900 at the end of 9 years, find the amount he borrowed.

Solution:
Let the borrowed sum be P.
SI for first 2 years + SI for next 3 years + SI for next 4 years = 20900
⇒ (P × 6 × 2/100) + (P × 9 × 3/100) + (P × 14 × 4/100) = 20900
⇒ (95P)/100 = 20900
⇒ P = (20900 × 100)/95
⇒ P = 22000
Therefore, Borrowed sum = Tk. 22000