Study Material — 3 PYQs (2020–2020) · Concept Notes · Shortcuts
SBI PO Basic Percentage is a frequently tested subtopic — 3 previous year questions from 2020–2020 papers are included below with concept notes, key rules and shortcut tricks.
3 questions from actual SBI PO papers · all shown free · click option to reveal solution
Exam Q 12020Previous Year Pattern
A number is increased by 25%, then decreased by 20%. If the final result is 600, what is the original number?
Exam Q 22020Previous Year Pattern
A person spends 30% of his income on rent, 25% on food, and 15% on transport. He saves the remaining amount. If his savings are ₹18,000, what is his total income?
Exam Q 32020Previous Year Pattern
In a college, 40% of students are in Science, 35% are in Commerce, and the remaining are in Arts. If 20% of Science students and 30% of Commerce students pass an entrance exam, what percentage of the total student population passes the exam?
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 mobile phone costs ₹15,000. During a sale, it is offered at 18% discount. What is the sale price of the mobile phone?
Practice 2easy
A student scored 72% in an exam and obtained 360 marks. What are the total marks of the exam?
Practice 3easy
The price of a book increased from ₹200 to ₹250. What is the percentage increase in price?
Practice 4easy
A factory produces 5000 units per month. If production increases by 12%, how many units will be produced in the next month?
Practice 5easy
A shopkeeper sells a shirt for ₹480, which is 20% more than its cost price. What is the cost price of the shirt?
Practice 6easy
In an election, candidate A received 55% of the votes and candidate B received the remaining votes. If the total number of votes cast was 8000, how many more votes did A receive than B?
Practice 7medium
A product's price was reduced by 20%, and then reduced again by 10%. What is the overall percentage reduction from the original price?
Practice 8medium
In an examination, a student scored 75% of the total marks. If the total marks were 320, how many marks did the student score?
Practice 9medium
A company's revenue increased from ₹40 lakhs to ₹50 lakhs. What is the percentage increase in revenue?
Practice 10medium
A shopkeeper marks an item at ₹500. He offers a discount of 12% on the marked price. What is the selling price of the item?
Practice 11medium
A student's marks increased from 60 to 75. What is the percentage increase in marks?
Practice 12medium
A bank account had ₹8,000 initially. After one year, it grew by 15%. How much money is in the account now?
Practice 13hard
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 is ₹800, what is his profit percentage?
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