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SSC CHSL Difference SI vs CI

Study Material — 1 PYQs (2018–2018) · Concept Notes · Shortcuts

SSC CHSL Difference SI vs CI is a frequently tested subtopic — 1 previous year questions from 2018–2018 papers are included below with concept notes, key rules and shortcut tricks.

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2018–2018
21 Practice
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8 Key Points
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Previous Year Questions

SSC CHSL Difference SI vs CI — Past Exam Questions

1 questions from actual SSC CHSL papers · all shown free · click option to reveal solution

Exam Q 12018Previous Year Pattern

Rajesh invests ₹8,000 at 10% per annum for 2 years. What is the difference between the compound interest and simple interest earned on this amount?

Concept Notes

Difference SI vs CI— Rules & Concept

Core ConceptRead this first — the foundation of the topic

The difference between Simple Interest (SI) and Compound Interest (CI) is one of the most frequently tested concepts in SSC CGL. This difference exists because compound interest includes interest on previously earned interest, while simple interest does not. Core Concept:

Simple Interest is calculated only on the principal amount throughout the investment period. Compound Interest is calculated on the principal plus accumulated interest from previous periods. The difference between CI and SI represents the 'extra earning' due to compounding effect.

Formula BlockMemorise — at least one formula appears in every paper
For 2 years: CI - SI = P × R² / (100)²
For 3 years: CI - SI = P × R² × (300 + R) / (100)³
Where P = Principal, R = Rate per annum, T = Time
Exam PatternsWhat examiners ask — read before attempting PYQs
SSC CGL typically asks three types of questions

(1) Direct calculation of difference given P, R, T (2) Finding principal when difference and rate are given (3) Finding rate when principal and difference are given. Most questions involve 2-3 years timeframe as longer periods make calculations complex

Powerful Shortcut for 2 Years

Difference = (SI for 1 year)² / Principal This works because: If SI for 1 year = PRT/100, then difference = (PRT/100)² / P = PR²T²/(100²P) = PR²/100² (for T=2)

Worked ExampleSolve this step-by-step before moving on
1
Step 1

Calculate SI for 2 years SI = (P × R × T) / 100 = (8000 × 15 × 2) / 100 = Rs. 2400

2
Step 2

Calculate CI for 2 years Amount = P(1 + R/100)ᵀ = 8000(1 + 15/100)² = 8000 × (1.15)² = 8000 × 1.3225 = Rs. 10,580 CI = Amount - Principal = 10,580 - 8000 = Rs. 2580

3
Step 3

Find difference CI - SI = 2580 - 2400 = Rs. 180 Alternative (Using Formula): CI - SI = P × R² / (100)² = 8000 × (15)² / (100)² = 8000 × 225 / 10000 = Rs. 180

ShortcutsUse these to save 30–60 seconds per question

for 3 Years: For 3 years, the difference equals: 3 × (2-year difference) + (2-year difference × R/100)

Exam TrapsCommon mistakes students make — avoid these

Students often confuse the formula for different time periods. Remember: the 2-year formula is simplest and most tested. For 3 years, don't memorize the complex formula - use the relationship with 2-year difference instead.

Key Points to Remember

  • Difference exists only when time period is more than 1 year
  • For 2 years: CI - SI = P × R² / (100)²
  • For 3 years: CI - SI = P × R² × (300 + R) / (100)³
  • Difference represents interest earned on interest portions
  • 2-year difference problems are most common in SSC CGL
  • If SI for 1 year is known, 2-year difference = (SI)² / Principal
  • Compound Interest is always greater than Simple Interest for same P, R, T
  • The difference increases exponentially with higher rates and longer periods

Exam-Specific Tips

  • For 2 years at 10% rate, difference is always 1% of principal
  • For 2 years at 20% rate, difference is always 4% of principal
  • For Rs. 100 at 15% for 2 years, difference is exactly Rs. 2.25
  • The ratio CI:SI for 2 years at 10% is always 21:20
  • For 3 years, minimum additional factor in formula is 300 (when R=0)
  • Difference for 2 years = P×R²/10000 (direct calculation)
  • For equal principal and rate, 3-year difference is roughly 3 times 2-year difference
  • At 25% rate for 2 years, difference equals 6.25% of principal
Practice MCQs

Difference SI vs CI — Practice Questions

21graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 21

All MCQs →
Practice 1easy

A principal of ₹10,000 is invested at 5% per annum. The difference between CI and SI after 3 years is:

Practice 2easy

The difference between compound interest and simple interest on a sum of ₹8,000 at 10% per annum for 2 years is:

Practice 3easy

At what rate of interest per annum will the difference between CI and SI on ₹5,000 for 2 years be ₹50?

Practice 4easy

If the difference between CI and SI on a sum for 2 years at 12% per annum is ₹144, what is the principal?

Practice 5easy

The simple interest on ₹4,000 for 2 years is ₹800. What will be the compound interest on the same sum at the same rate for the same period?

Practice 6easy

A principal of ₹10,000 is invested at 5% per annum. What is the difference between compound interest and simple interest after 3 years?

Practice 7easy

The difference between compound interest and simple interest on a certain sum at 8% per annum for 2 years is ₹64. What is the principal?

Practice 8easy

The difference between CI and SI on ₹6,000 at 8% per annum for 2 years is ₹x. Find the value of x.

Practice 9medium

A principal amount is invested at 20% per annum. The difference between compound interest for 2 years and simple interest for 2 years is ₹800. What is the principal?

Practice 10medium

The difference between compound interest and simple interest on a principal for 3 years at 5% per annum is ₹61.25. What is the principal?

Practice 11medium

The difference between compound interest and simple interest on a sum of money for 2 years at 10% per annum is ₹40. Find the principal.

Practice 12medium

The difference between CI and SI on a certain sum for 2 years at 5% per annum is ₹12.50. What is the principal?

Practice 13medium

A sum of money becomes ₹6050 in 2 years and ₹6655 in 3 years under compound interest. Find the rate of interest per annum.

Practice 14medium

A sum of money amounts to ₹2,640 in 2 years at 10% per annum under simple interest. What will be the difference between simple interest and compound interest on the same sum for the same period and rate?

Practice 15medium

A principal becomes ₹5,500 in 2 years and ₹6,050 in 3 years under compound interest. What is the rate of interest per annum?

Practice 16medium

The simple interest on a sum for 2 years at 12% per annum is ₹2,880. If the same sum is invested at the same rate for the same period under compound interest, how much more interest will be earned?

Practice 17hard

The difference between compound interest and simple interest on a sum for 2 years at a certain rate per annum is ₹400. If the rate of interest is 20% per annum, what is the principal?

Practice 18hard

A person invests ₹8,000 at 15% per annum for 2 years under compound interest. Another person invests the same amount at 15% per annum for 2 years under simple interest. What is the difference between the amounts they receive?

Practice 19hard

The difference between compound interest and simple interest on a certain principal for 2 years at 12% per annum is ₹144. If the same principal is invested at 10% per annum for 3 years under compound interest, what will be the compound interest earned?

Practice 20hard

A sum of ₹5,000 is invested at 12% per annum. The difference between compound interest for 2 years and simple interest for 2 years is ₹X. If the same sum is invested at 12% per annum for 3 years, the difference between CI and SI becomes ₹Y. What is the value of (Y - X)?

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60-Second Revision — Difference SI vs CI

  • Formula: 2 years difference = P × R² / 10000
  • Remember: Difference exists only when T > 1 year
  • Trick: 2-year difference = (Annual SI)² / Principal
  • Pattern: Most SSC questions use 2-3 year timeframes
  • Trap: Don't use 3-year formula for 2-year problems
  • Quick check: At 10% for 2 years, difference = 1% of principal
  • Method: Calculate both CI and SI separately when formulas confuse
←Compound InterestHalf-Yearly / Quarterly CI→
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