Simple Interest

“Simple Interest is widely used in banking, finance, and aptitude exams like SSC, RRB, Banking, and other competitive exams.”

1. Basic Concepts and Formulas

  • Simple Interest (SI) = (Principal × Rate × Time) / 100
  • Amount (A) = Principal + Interest
  • Principal (P) = (SI × 100) / (Rate × Time)
  • Rate (R) = (SI × 100) / (Principal × Time)
  • Time (T) = (SI × 100) / (Principal × Rate)

2. Type-Wise Questions

  • Type 1: Basic SI Calculation
    Example: Calculate the simple interest on ₹2000 for 3 years at 5% p.a.
    SI = (2000 × 5 × 3) / 100 = ₹300
  • Type 2: Find Principal
    Example: The simple interest on ₹4000 for 5 years at 8% p.a. is ₹1600. Find the principal.
    P = (1600 × 100) / (8 × 5) = ₹4000
  • Type 3: Find Rate
    Example: ₹1500 earns ₹300 as interest in 2 years. What is the rate of interest?
    R = (300 × 100) / (1500 × 2) = 10%
  • Type 4: Find Time
    Example: ₹2000 earns ₹300 as interest at 6% p.a. for how long?
    T = (300 × 100) / (2000 × 6) = 2.5 years
  • Type 5: Find Amount
    Example: ₹4000 is invested for 2 years at 5% per annum. Find the amount.
    A = 4000 + (4000 × 5 × 2) / 100 = ₹4400
  • Type 6: Interest Earned from a Fixed Deposit
    Example: A person deposits ₹10,000 in a bank for 3 years at 8% per annum simple interest. Calculate the interest earned.
    SI = (10000 × 8 × 3) / 100 = ₹2400
  • Type 7: Amount after Simple Interest
    Example: If ₹2000 is invested at 10% for 4 years, what will be the total amount?
    A = 2000 + (2000 × 10 × 4) / 100 = ₹2800
  • Type 8: Profit Calculation
    Example: A sum of ₹5000 is invested for 2 years at 7% per annum. Calculate the profit (Interest).
    SI = (5000 × 7 × 2) / 100 = ₹700
  • Type 9: Principal Given Amount and Interest
    Example: Find the principal amount if the simple interest earned on ₹8000 for 5 years at 10% p.a. is ₹4000.
    P = (4000 × 100) / (10 × 5) = ₹8000
  • Type 10: Time Given Amount and SI
    Example: ₹2000 earns ₹400 as interest in 5 years. Find the rate.
    R = (400 × 100) / (2000 × 5) = 4%
  • Type 11: Calculate Interest on a Loan
    Example: Calculate the interest on ₹1500 for 2 years at 6% per annum.
    SI = (1500 × 6 × 2) / 100 = ₹180
  • Type 12: Calculate the Time for Double the Money
    Example: How much time will ₹2500 take to double at 8% per annum simple interest?
    Time = (2500 × 100) / (2500 × 8) = 12.5 years
  • Type 13: Calculate Principal with Compound Interest Concept
    Example: ₹1200 is invested for 3 years at 6% p.a., find the principal.
    P = SI × 100 / (R × T) = ₹1200
  • Type 14: Find Amount when SI and P are Given
    Example: Find the amount if the principal is ₹1500, and the interest is ₹450 at 10% for 3 years.
    A = 1500 + 450 = ₹1950
  • Type 15: Interest on a Savings Account
    Example: A person deposits ₹5000 in a savings account for 3 years at 4% p.a. Calculate the interest earned.
    SI = (5000 × 4 × 3) / 100 = ₹600
  • Type 16: Find the Total Interest for a Given Principal
    Example: ₹2500 earns ₹500 as interest in 2 years. What is the rate of interest?
    R = (500 × 100) / (2500 × 2) = 10%
  • Type 17: Find the Difference in Interest
    Example: ₹4000 is invested at 6% for 3 years. Compare the simple interest with ₹5000 invested at 5% for 3 years.
    SI for ₹4000 = 4000 × 6 × 3 / 100 = ₹720
    SI for ₹5000 = 5000 × 5 × 3 / 100 = ₹750
    Difference = ₹750 - ₹720 = ₹30
  • Type 18: Find Rate from Amount
    Example: If ₹1000 becomes ₹1200 in 3 years, find the rate.
    R = (200 × 100) / (1000 × 3) = 6.67%
  • Type 19: Compound Interest Equivalent to SI
    Example: Compare compound interest and simple interest for ₹1000 at 5% for 2 years.
    CI = SI (when time and rate are same for both)
  • Type 20: Total Interest Earned on Loan
    Example: Calculate the interest on ₹5000 for 4 years at 7% p.a.
    SI = (5000 × 7 × 4) / 100 = ₹1400
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