Study Material — 19 PYQs (2018–2020) · Concept Notes · Shortcuts
RRB NTPC Percentage Change is a frequently tested subtopic — 19 previous year questions from 2018–2020 papers are included below with concept notes, key rules and shortcut tricks.
19 questions from actual RRB NTPC papers · all shown free · click option to reveal solution
Exam Q 12020Previous Year Pattern
The value of a car depreciates from ₹8,00,000 to ₹6,40,000. What is the percentage depreciation?
Exam Q 22020Previous Year Pattern
A shopkeeper increases the price of a shirt from ₹400 to ₹500. What is the percentage increase in price?
Exam Q 32020Previous Year Pattern
The population of a town decreases from 80,000 to 60,000. What is the percentage decrease?
Exam Q 42020Previous Year Pattern
A student scored 45 marks out of 60 in an exam. In the next exam, the student scores 54 marks out of 60. What is the percentage increase in marks?
Exam Q 52020Previous Year Pattern
The price of a commodity was ₹250. After a discount, it becomes ₹200. What is the percentage discount?
Exam Q 62020Previous Year Pattern
A worker's salary increased from ₹18,000 to ₹22,500. What is the percentage increase in salary?
Exam Q 72020Previous Year Pattern
A company's revenue was ₹10 lakhs in 2021. In 2022, it decreased by 25%, and in 2023, it increased by 40%. What is the revenue in 2023?
Exam Q 82018Previous Year Pattern
The price of a commodity increased by 25% in the first year and then decreased by 20% in the second year. If the final price is ₹1,200, what was the original price?
Exam Q 92020Previous Year Pattern
The price of petrol decreased by 15% and then increased by 20%. If the final price is ₹102 per litre, what was the original price?
Exam Q 102020Previous Year Pattern
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?
Exam Q 112020Previous Year Pattern
A shopkeeper buys goods for ₹800. He marks up the price by 50% and then offers a discount of 30% on the marked price. What is his profit or loss percentage?
Exam Q 122020Previous Year Pattern
The population of a town was 50,000 in 2020. It increased by 20% in 2021 and by 10% in 2022. What was the population at the end of 2022?
Exam Q 132020Previous Year Pattern
A student's marks increased from 60 to 75. What is the percentage increase in marks?
Exam Q 142020Previous Year Pattern
A product's price increases by 25% in the first year. In the second year, the new price decreases by 20%. If the original price was ₹800, what is the net percentage change in price over the two years?
Exam Q 152020Previous Year Pattern
A quantity X increases by 30%, then decreases by 30%. A quantity Y increases by 20%, then increases by 25%. Which statement is correct?
Exam Q 162020Previous Year Pattern
A worker's salary increases by 15% in January. In February, due to company policy, all salaries are reduced by 10%. In March, the worker receives a bonus that increases his salary by 8%. If his original salary was ₹20,000, what is his final salary after all three changes?
Exam Q 172020Previous Year Pattern
A shopkeeper increases the cost price of an item by 40% to set the marked price. He then offers a discount of 25% on the marked price. If the cost price is ₹500, what is the profit percentage?
Exam Q 182020Previous Year Pattern
The price of a commodity increases by 25%. To bring it back to the original price, by what percentage should it be reduced?
Exam Q 192020Previous Year Pattern
The population of a city increases by 20% in the first year and by 10% in the second year. If the population decreases by 15% in the third year, what is the net percentage change in population over three years?
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 by 20% in one year. If the population is now 32,000, what was the population one year ago?
Practice 2easy
If the price of sugar increased by 15%, and the new price is ₹69 per kg, what was the original price per kg?
Practice 3easy
The population of a town decreased by 10% in one year. If the population is now 45,000, what was the population one year ago?
Practice 4easy
The salary of an employee increased by 20%. If the new salary is ₹36,000, what was the original salary?
Practice 5easy
The price of a book increased from ₹200 to ₹250. What is the percentage increase in price?
Practice 6easy
A number increased by 25% becomes 500. What is the original number?
Practice 7easy
A shopkeeper reduced the price of a shirt from ₹800 to ₹600. What is the percentage decrease?
Practice 8medium
The population of a town was 80,000 in 2020. It increased by 15% in 2021 and then decreased by 10% in 2022. What was the population at the end of 2022?
Practice 9medium
A student's marks increased from 60 to 75 in an exam. What is the percentage increase in marks?
Practice 10medium
A shopkeeper buys goods at ₹500 per unit. He increases the price by 40% and then offers a discount of 25% on the marked price. What is the selling price per unit, and what is his profit percentage?
Practice 11medium
A student's marks increased from 60 to 75. What is the percentage increase in marks?
Practice 12medium
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 the price over the two years?
Practice 13medium
A product's price was ₹800. It was increased by 25% and then decreased by 25%. What is the final price?
Practice 14medium
A shopkeeper reduces the price of an item by 30%. If the new price is ₹350, what was the original price?
Practice 15hard
The price of a commodity increases by 25% in the first year. In the second year, it decreases by 20% of the new price. In the third year, it increases by 10% of the price at the end of year 2. If the original price was ₹800, what is the percentage change in price over the three years?
Practice 16hard
A number is increased by 20%, then decreased by 20%. The result is 384. What is the original number?
Practice 17hard
A student's test score increased by 30% from Test 1 to Test 2. From Test 2 to Test 3, the score decreased by 20%. If the score in Test 3 is 312 marks, what was the score in Test 1? Additionally, by what percentage did the score change from Test 1 to Test 3?
Practice 18hard
A product's price increased by 25% in the first year. In the second year, the new price decreased by 20%. If the final price is ₹1,200, what was the original price?
Practice 19hard
A shopkeeper marks up goods by 40% above cost price. He then offers a 25% discount on the marked price. If the cost price is ₹800, what is his profit percentage?
Practice 20hard
A shopkeeper marks up goods by 60% above cost price. He then offers a discount of 25% on the marked price. Later, due to a supply shortage, he increases the selling price by 20%. What is the overall percentage profit or loss on the cost price?