Study Material — 15 PYQs (2019–2019) · Concept Notes · Shortcuts
SSC CPO Basic Percentage is a frequently tested subtopic — 15 previous year questions from 2019–2019 papers are included below with concept notes, key rules and shortcut tricks.
15 questions from actual SSC CPO papers · all shown free · click option to reveal solution
Exam Q 12019Previous Year Pattern
What is 18% of 250?
Exam Q 22019Previous Year Pattern
If a price increases from ₹200 to ₹250, what is the percentage increase?
Exam Q 32019Previous Year Pattern
A number is increased by 25%. If the new number is 500, what was the original number?
Exam Q 42019Previous Year Pattern
In an exam, 65% of students passed. If 390 students passed, how many students appeared in total?
Exam Q 52019Previous Year Pattern
A shopkeeper marks an item at ₹500. He offers a 20% discount. What is the selling price?
Exam Q 62019Previous Year Pattern
If 45% of a number is 360, what is the number?
Exam Q 72019Previous Year Pattern
A person spends 30% of his income on rent, 25% on food, and 15% on transport. If he saves ₹1,800 per month, which is the remaining percentage of his income, what is his total monthly income?
Exam Q 82019Previous Year Pattern
A shopkeeper marks his goods 40% above the cost price. If he gives a discount of 20% on the marked price, what is his profit percentage?
Exam Q 92019Previous Year Pattern
A student scored 45% in an exam and failed by 30 marks. If he had scored 55%, he would have passed by 10 marks. What is the passing percentage?
Exam Q 102019Previous Year Pattern
A number is increased by 25%, and then the result is decreased by 20%. What is the net change in the number as a percentage?
Exam Q 112019Previous Year Pattern
In an examination, 35% of students failed in Mathematics, 25% failed in English, and 10% failed in both subjects. What percentage of students passed in both subjects?
Exam Q 122019Previous Year Pattern
The price of a commodity increases by 15% in the first year and decreases by 10% in the second year. If the price at the end of the second year is ₹2,070, what was the original price?
Exam Q 132019Previous Year Pattern
In an election, candidate A received 45% of votes, candidate B received 35% of votes, and the remaining votes were invalid. If the total number of valid votes was 8000, how many invalid votes were cast?
Exam Q 142019Previous Year Pattern
A number is increased by 20%, then the result is decreased by 20%. What is the net change in the original number as a percentage?
Exam Q 152019Previous Year Pattern
A shopkeeper marks up goods by 60% above cost price. He then offers a discount of 25% on the marked price. If the cost price of an item is ₹400, what is his profit percentage?
Concept Notes
Basic Percentage— Rules & Concept
Core ConceptRead this first — the foundation of the topic
Basic Percentage is the foundation of all percentage problems in SSC CGL. It measures parts per hundred. The word 'percent' comes from Latin 'per centum' meaning 'by hundred'. Understanding this concept is crucial as it appears in 2-3 questions in every SSC CGL paper. Core Concept: Percentage is a way to express a fraction with denominator 100. When you say 25%, it means 25 out of 100 parts. Think of it as cutting a pie into 100 equal slices and taking some of them.
Key RulesCore rules you must know cold
First, percentage is always calculated on a base value. Second, 100% means the complete quantity. Third, percentages can exceed 100% when the part is larger than the whole. Fourth, percentage change and percentage of a number are different concepts.
Formula BlockMemorise — at least one formula appears in every paper
• Percentage = (Part/Whole) × 100
• Part = (Percentage/100) × Whole
• Whole = (Part × 100)/Percentage
• Percentage to Fraction: x% = x/100
• Percentage to Decimal: x% = x/100 = 0.0x
Exam PatternsWhat examiners ask — read before attempting PYQs
Powerful Shortcuts for Quick Calculation
Shortcut 1 - Common Percentage Conversions:
• 50% = 1/2, 25% = 1/4, 20% = 1/5, 10% = 1/10
• 33.33% = 1/3, 66.67% = 2/3, 12.5% = 1/8, 16.67% = 1/6
Memorize these to solve faster without calculations
Shortcut 2 - Quick Mental Math Trick
• For 15% of any number: Take 10% + 5%
• For 35% of any number: Take 30% + 5%
• Break complex percentages into easier chunks
Worked ExampleSolve this step-by-step before moving on
1
Step 1
Convert percentage to decimal: 24% = 24/100 = 0.24
Add: 170 + 34 = 204
Answer: 24% of 850 = 204
Worked Example 2: What percentage is 156 of 240?
1
Step 1
Use formula: Percentage = (Part/Whole) × 100
2
Step 2
Substitute values: (156/240) × 100
3
Step 3
Simplify fraction: 156/240 = 13/20 (dividing by 12)
4
Step 4
Convert to decimal: 13/20 = 0.65
5
Step 5
Multiply by 100: 0.65 × 100 = 65%
Answer: 156 is 65% of 240
Shortcut 3 - The Unitary Method for Percentages:
If x% = y, then 1% = y/x, and 100% = (y × 100)/x
This eliminates complex calculations in competitive exams.
Exam TrapsCommon mistakes students make — avoid these
- The #1 Trap: Students confuse 'percentage of' with 'percentage more than'. For example, if A is 20% of B, it does NOT mean A is 20% more than B. '20% of B' means A = 0.20 × B. But '20% more than B' means A = B + 0.20 × B = 1.20 × B.
This confusion costs precious marks in exams.
Another frequent error is forgetting to convert percentage back to the required form. Always check if the answer needs to be in percentage, decimal, or fraction format.
Key Points to Remember
Percentage means parts per hundred, always calculated on a base value
A student scored 65% in Mathematics and 72% in English. If Mathematics carries a weight of 3 and English carries a weight of 2, what is the weighted average percentage?
Practice 2hard
A product's price is increased by 15%, then decreased by 10%, then increased by 20%. If the original price was ₹1000, what is the final price?
Practice 3hard
A container has 240 litres of a mixture of milk and water in the ratio 5:3. If 48 litres of the mixture is removed and replaced with pure milk, what is the percentage of milk in the new mixture?
60-Second Revision — Basic Percentage
Remember: Percentage = (Part/Whole) × 100 for all basic problems
Formula: Part = (Percentage/100) × Whole for finding quantities
Trap: 'x% of y' ≠ 'x% more than y' - completely different meanings
Shortcut: Use fraction conversions (25% = 1/4) for faster calculations
Quick check: 50% should always give exactly half the original number