0
0

Basic SI Calculation

Introduction

Simple Interest (SI) वह extra पैसा है जो किसी principal amount पर एक fixed rate पर कुछ समय के लिए दिया या कमाया जाता है। यह interest वाले problems का सबसे basic concept है और आगे आने वाले advanced patterns की foundation भी यही है।

Pattern: Basic SI Calculation

Pattern

Formula है: SI = (P × R × T) / 100

जहाँ:
P = Principal (initial amount)
R = Rate of interest (per annum)
T = Time (years में)

Step-by-Step Example

Question

₹5000 पर 10% per annum की दर से 2 years के लिए Simple Interest निकालें।

Options:
A. ₹800
B. ₹900
C. ₹1000
D. ₹1200

Solution

  1. Step 1: Values पहचानें

    P = 5,000, R = 10%, T = 2 years.

  2. Step 2: Formula apply करें

    SI = (P × R × T) / 100.

  3. Step 3: Interest calculate करें

    SI = (5,000 × 10 × 2) / 100 = 1,000.

  4. Final Answer:

    ₹1,000 → Option C

  5. Quick Check:

    1 year का interest = 10% of 5,000 = 500. 2 years → 500 × 2 = 1,000 ✅

Quick Variations

1. Time period change हो सकता है (months → years में convert करें)।

2. Fractional years भी दिए जा सकते हैं (जैसे 6 months = 0.5 years)।

3. कभी-कभी total amount पूछा जाता है = Principal + SI.

Trick to Always Use

  • Step 1 → Formula clearly लिखें।
  • Step 2 → Values direct plug करें, shortcuts से बचें।
  • Step 3 → Months दिए हों तो पहले उन्हें years में convert करें।

Summary

Summary

  • सभी simple interest questions में SI = (P × R × T) / 100 formula use करें।
  • P को rupees में, R को percent में और T को years में रखें।
  • Months को हमेशा years में बदलें।
  • Verify करने के लिए yearly interest × number of years देखें।

याद रखने लायक example:
₹5,000 पर 10% per annum से 2 years में SI = ₹1,000.

Practice

(1/5)
1. Find the Simple Interest on ₹2000 at 5% per annum for 2 years.
easy
A. 200
B. 250
C. 180
D. 300

Solution

  1. Step 1: Note the given values

    P = 2,000, R = 5%, T = 2.

  2. Step 2: Apply the SI formula

    SI = (P × R × T)/100 = (2,000 × 5 × 2)/100.

  3. Step 3: Calculate the interest

    SI = 200.

  4. Final Answer:

    200 → Option A

  5. Quick Check:

    Yearly interest = 2,000 × 5% = 100; for 2 years → 100 × 2 = 200 ✅
Hint: Multiply the yearly interest (P×R/100) by the number of years.
Common Mistakes: Forgetting to convert rate/time or dividing by 2 instead of multiplying time.
2. Calculate the SI on ₹4000 at 8% per annum for 1 year.
easy
A. 280
B. 320
C. 300
D. 360

Solution

  1. Step 1: Write the known values

    P = 4,000, R = 8%, T = 1.

  2. Step 2: Apply SI formula

    SI = (4,000 × 8 × 1)/100 = 320.

  3. Final Answer:

    320 → Option B

  4. Quick Check:

    8% of 4,000 = 0.08 × 4,000 = 320 ✅
Hint: For 1 year, use SI = (P × R) / 100 directly.
Common Mistakes: Forgetting that time = 1 year or using incorrect rate conversion.
3. Find the SI on ₹6000 at 12% per annum for 6 months.
easy
A. 720
B. 600
C. 500
D. 360

Solution

  1. Step 1: Convert time properly

    P = 6,000, R = 12%, T = 6 months = 0.5 year.

  2. Step 2: Use SI formula

    SI = (6,000 × 12 × 0.5)/100.

  3. Step 3: Perform the calculation

    SI = (6,000 × 6)/100 = 360.

  4. Final Answer:

    360 → Option D

  5. Quick Check:

    Yearly SI = 12% of 6,000 = 720; half-year = 720 ÷ 2 = 360 ✅
Hint: Convert months to years (6 months = 0.5 year) before applying the formula.
Common Mistakes: Taking 6 months as 6 years or forgetting to divide by 12.
4. A sum of ₹5000 is lent at 9% per annum for 4 years. Find the Simple Interest.
medium
A. 1800
B. 1600
C. 1400
D. 2000

Solution

  1. Step 1: Extract the values

    P = 5,000, R = 9%, T = 4.

  2. Step 2: Apply the SI formula

    SI = (5,000 × 9 × 4)/100.

  3. Step 3: Calculate SI

    SI = (5,000 × 36)/100 = 1,800.

  4. Final Answer:

    1,800 → Option A

  5. Quick Check:

    Yearly SI = 5,000 × 9% = 450; for 4 years → 450 × 4 = 1,800 ✅
Hint: Compute yearly interest first (P×R/100), then multiply by years.
Common Mistakes: Mixing up principal and total amount or adding principal to SI.
5. If ₹8000 is invested at 7.5% per annum for 3 years, what is the Simple Interest?
medium
A. 1600
B. 1700
C. 1800
D. 2000

Solution

  1. Step 1: Identify P, R, and T

    P = 8,000, R = 7.5%, T = 3.

  2. Step 2: Apply SI formula

    SI = (8,000 × 7.5 × 3)/100.

  3. Step 3: Compute the value

    SI = (8,000 × 22.5)/100 = 1,800.

  4. Final Answer:

    1,800 → Option C

  5. Quick Check:

    Yearly SI = 7.5% of 8,000 = 600; for 3 years → 600 × 3 = 1,800 ✅
Hint: Convert decimal % (7.5%) correctly as 7.5 before multiplying.
Common Mistakes: Rounding 7.5% incorrectly or forgetting to multiply by 3 years.

Mock Test

Ready for a challenge?

Take a 10-minute AI-powered test with 10 questions (Easy-Medium-Hard mix) and get instant SWOT analysis of your performance!

10 Questions
5 Minutes