1. A principal of 8,000 is invested at 1.5% a month for 10 months. What is the amount?
- Input
- 8000 | 1,5% | 10
- Expected output
- 9200
I = 8,000 × 0.015 × 10 = 1,200. A = 8,000 + 1,200 = 9,200.
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simple interest solved exercises
Simple interest exercises follow a few molds: find the interest or the amount, find the time, find the rate, discount a note and compute a delay. Solve each statement on paper and check the answer below; then swap the numbers in the calculator to practice variations.
I = 8,000 × 0.015 × 10 = 1,200. A = 8,000 + 1,200 = 9,200.
t = 600 ÷ (2,500 × 0.024) = 600 ÷ 60 = 10 months.
I = 900. r = 900 ÷ (4,000 × 5) = 0.045 = 4.5% a month.
Bank: D = 10,000 × 0.03 × 3 = 900 (net 9,100). True: D = 900 ÷ 1.09 = 825.69 (net 9,174.31).
Fee: 1,500 × 0.02 = 30. Interest: 1,500 × (0.01 ÷ 30) × 30 = 15. Total: 1,500 + 30 + 15 = 1,545.
I = P × r × t, where P is the principal, r the rate per period (as a decimal, 2% = 0.02) and t the number of periods, always in the same unit as the rate. The amount is A = P + I = P × (1 + r × t). Example: 1,000 at 2% per month for 6 months earns I = 1,000 × 0.02 × 6 = 120, and the amount is 1,120.
The statement should say "simple interest" or "simple capitalization". If it does not, the convention of the study material or exam board rules, and the right move is to check with whoever wrote the question. When in doubt, solve in both regimes in the Simple vs compound tab and see which one matches the answer key.
Convert time to months by dividing days by 30 (commercial basis) or the rate to per day by dividing by 30. On 1,000 at 3% a month for 45 days: t = 1.5 months and I = 1,000 × 0.03 × 1.5 = 45. The Units and dates tab does the conversion and shows the difference between day-count bases.
Use it to check and understand the working, not to memorize. In an exam, the answer key follows the exam board's convention (360-day commercial year, requested rounding). The calculator rounds money to the cent only at the end, which usually matches answer keys.