Radhika borrowed ₹ 12000 from her friends. Out of which ₹ 4000 were borrowed at 18% and the remaining at 15% rate of interest per annum. What is the total interest after 3 years? 

Interest Calculation for Radhika's Loan

1. Interest Calculation for ₹4000 at 18%:

• Radhika borrowed ₹4000 at an 18% annual interest rate.
• Interest for one year is calculated as: Principal x Rate x Time.
• Here, Principal = ₹4000, Rate = 18% (or 0.18), Time = 1 year.
• Interest for one year: ₹4000 x 0.18 x 1 = ₹720.
• For 3 years: ₹720 x 3 = ₹2160.

2. Interest Calculation for the Remaining Amount at 15%:

• The remaining amount is ₹12000 - ₹4000 = ₹8000.
• This is borrowed at a 15% annual interest rate.
• Interest for one year on ₹8000: ₹8000 x 0.15 x 1 = ₹1200.
• For 3 years: ₹1200 x 3 = ₹3600.

3. Total Interest:

• Total interest is the sum of interest from both parts.
• From ₹4000 at 18%: ₹2160.
• From ₹8000 at 15%: ₹3600.
• Total Interest: ₹2160 + ₹3600 = ₹5760.