Study Material — 5 PYQs (2020–2020) · Concept Notes · Shortcuts
SSC MTS Percentage Change is a frequently tested subtopic — 5 previous year questions from 2020–2020 papers are included below with concept notes, key rules and shortcut tricks.
5 questions from actual SSC MTS papers · all shown free · click option to reveal solution
Exam Q 12020Previous Year Pattern
A population decreased by 20% in Year 1. To return to its original size by the end of Year 2, by what percentage must it increase in Year 2?
Exam Q 22020Previous Year Pattern
A company's revenue increased by 40% in Year 1, then decreased by 30% in Year 2. If the revenue at the end of Year 2 was ₹98 lakhs, what was the initial revenue?
Exam Q 32020Previous Year Pattern
The price of petrol increased by 15% in the first quarter and by 12% in the second quarter. By what percentage did the price increase over the two quarters combined?
Exam Q 42020Previous Year Pattern
A student's marks increased from 320 to 400. Later, the marks were recalculated and decreased by 10%. What is the net percentage change from the original marks of 320?
Exam Q 52020Previous Year Pattern
A product's cost price is ₹500. The shopkeeper marks it up by 60%, then offers a discount of 25% on the marked price. What is the profit percentage?
Concept Notes
Percentage Change— Rules & Concept
Core ConceptRead this first — the foundation of the topic
Percentage change is the difference between the original value and the new value, expressed as a percentage of the original value. This concept appears in almost every SSC CGL paper and forms the backbone of profit-loss, simple interest, and data interpretation questions. Core Concept: When any quantity increases or decreases, we calculate the percentage change to measure the rate of change. For example, if your salary increases from Rs 20,000 to Rs 25,000, the percentage increase is 25%.
Formula BlockMemorise — at least one formula appears in every paper
Block:
• Percentage Increase = [(New Value - Original Value) / Original Value] × 100
• Percentage Decrease = [(Original Value - New Value) / Original Value] × 100
• New Value after x% increase = Original Value × (100 + x)/100
• New Value after x% decrease = Original Value × (100 - x)/100
• Successive percentage changes: If a value changes by a% then b%, final change = [a + b + (ab/100)]%
Exam PatternsWhat examiners ask — read before attempting PYQs
SSC loves asking percentage change in population growth, salary hikes, price fluctuations, and successive discounts. Questions often involve finding original values when final values and percentage changes are given.
ShortcutsUse these to save 30–60 seconds per question
1
Two successive increases of x% = (x + x + x²/100)% total increase
2
One increase of x% followed by decrease of x% = (x²/100)% net decrease
3
25% increase means multiply by 1.25
4
20% decrease means multiply by 0.8
5
12.5% increase means multiply by 9/8
Worked ExampleSolve this step-by-step before moving on
1
Step 1
Identify original value = 50,000, new value = 65,000
2
Step 2
Find increase = 65,000 - 50,000 = 15,000
3
Step 3
Apply formula = (15,000/50,000) × 100 = 30%
Answer: 30% increase
Worked Example 2:
A number is first increased by 20% and then decreased by 15%. Find the overall percentage change.
1
Step 1
Let original number = 100 (always take 100 for easier calculation)
2
Step 2
After 20% increase = 100 × 1.2 = 120
3
Step 3
After 15% decrease = 120 × 0.85 = 102
4
Step 4
Overall change = 102 - 100 = 2
5
Step 5
Percentage change = 2% increase
Alternative: Using formula = 20 + (-15) + (20×(-15)/100) = 20 - 15 - 3 = 2% increase
Shortcut Trick #3: Percentage to fraction conversions:
• 12.5% = 1/8, 16.67% = 1/6, 33.33% = 1/3, 66.67% = 2/3
• These help in quick mental calculations during exams.
Exam TrapsCommon mistakes students make — avoid these
#1: Students often confuse which value to use as base. Remember: percentage change is always calculated on the ORIGINAL value, not the new value. If price changes from Rs 100 to Rs 120, the base is Rs 100, not Rs 120.
Many students calculate (20/120) × 100 instead of (20/100) × 100, leading to wrong answers.
Exam Strategy: Practice reverse calculations where you find original values from final values and percentage changes. SSC frequently tests this concept in tricky word problems involving multiple successive changes.
Key Points to Remember
Percentage change = [(New Value - Original Value) / Original Value] × 100
Always use original value as denominator, never the new value
Successive changes formula: a + b + (ab/100) for changes of a% and b%
The population of a town decreased from 50,000 to 45,000. What is the percentage decrease in population?
Practice 2easy
A product's price was increased by 25% and then decreased by 20%. What is the net percentage change in price?
Practice 3easy
A shopkeeper reduced the price of a shirt from ₹800 to ₹600. What is the percentage decrease?
Practice 4easy
The price of a book increased from ₹200 to ₹250. What is the percentage increase in price?
Practice 5easy
A number increased by 20% gives 360. What is the original number?
Practice 6medium
A retailer increases the price of an item by 30% and then gives a discount of 30% on the new price. A customer claims he gets the item at the original price. Is the customer correct?
Practice 7medium
The price of a commodity increases by 25% in the first year and then decreases by 20% in the second year. What is the net percentage change in price over the two years?
Practice 8medium
A shopkeeper buys goods at ₹800 per unit. He marks up the price by 40% but then offers a 25% discount on the marked price. What is the percentage profit or loss?
Practice 9medium
The value of a car depreciates by 15% in the first year and by 10% in the second year. If the car's value after two years is ₹1,53,000, what was its original value?
Practice 10hard
A shopkeeper increases the price of an item by 25%, then due to poor sales, reduces the new price by 20%. If the final price is ₹600, what was the original price?