Nalanda College, Colombo 10 Grade 11 Maths Worksheet: 9 Percentages

Simple interest on a loan for two years

Answer: Rs. 1600

💡 What it's asking: Simple interest means the interest is always worked out on the original loan, so you pay the same amount of interest every year. Find one year's interest and multiply by the number of years.

1. 1One year's interest = 10% of Rs. 8000 = 10/100 × 8000 = Rs. 800.
2. 2The loan is for 2 years and each year's interest is the same.
3. 3Total interest = 2 × 800 = Rs. 1600.
4. 4The formula I = P × R × T ÷ 100 = 8000 × 10 × 2 ÷ 100 gives the same Rs. 1600.

✅ Rs. 1600 is 20% of Rs. 8000, which matches 10% a year for 2 years.

Annual simple interest rate from loan and amount repaid

Answer: 12% per year

💡 What it's asking: The amount paid back includes the loan plus the interest. Take the loan away to get the interest, find one year's share, then turn it into a percentage of the loan.

1. 1Interest for 3 years = 40 800 − 30 000 = Rs. 10 800.
2. 2Interest for one year = 10 800 ÷ 3 = Rs. 3600.
3. 3Write it as a percentage of the loan: 3600 ÷ 30 000 × 100 = 12%.
4. 4So the rate is 12% per year.

✅ 12% of 30 000 = 3600, and 3600 × 3 = 10 800; add the loan and you get 40 800.