% Shortcuts · 10 percentage tricks for exams
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Quick Note
"Time is the difference between a good score and a great score." Every competitive exam has one thing in common: Percentage problems. You don't need to be a math wizard — you just need shortcut tricks. This guide walks you through 10 proven percentage shortcuts that will save you minutes on your aptitude test.
▣ Why Percentage Shortcuts Matter
A typical aptitude test gives you 60–90 seconds per question. If you solve a percentage problem the "long way" (writing fractions, multiplying decimals), you lose precious time.
🎯 The Goal:
Turn percentage problems into simple mental math.
▣ The Foundation: Fraction ↔ Percentage Table
You must memorize this table. It is the key to all shortcuts.
| Fraction | Percentage | Fraction | Percentage |
|---|---|---|---|
| 1/1 | 100% | 1/6 | 16.67% |
| 1/2 | 50% | 1/7 | 14.28% |
| 1/3 | 33.33% | 1/8 | 12.5% |
| 1/4 | 25% | 1/9 | 11.11% |
| 1/5 | 20% | 1/10 | 10% |
| 1/20 | 5% | 1/25 | 4% |
Example: If you need 25% of 200, and you know 25% = 1/4, then 200 ÷ 4 = 50. Done.
▣ Shortcut 1: The Swapping Trick
x% of y = y% of x
This single trick can turn a difficult calculation into an easy one.
Example 1
Problem: What is 8% of 250?
Long way:
8/100 × 250 = 20
⚡ Shortcut:
Swap → 250% of 8 = 2.5 × 8 = 20
Example 2
Problem: What is 12% of 50?
⚡ Shortcut:
Swap → 50% of 12 = 6
▣ Shortcut 2: The 10% / 1% Split Method
Concept: Break any percentage into easy parts: 10%, 1%, 5%, etc.
- 10% of a number = Move decimal one place left
- 1% of a number = Move decimal two places left
- 5% of a number = 10% ÷ 2
Example 3
Problem: Find 23% of 400.
10% of 400 = 40
20% of 400 = 80
1% of 400 = 4
3% of 400 = 12
⚡ Shortcut:
23% of 400 = 20% + 3% = 80 + 12 = 92
Example 4
Problem: Find 47% of 500.
⚡ Shortcut:
50% of 500 = 250, 3% of 500 = 15
47% of 500 = 50% − 3% = 250 − 15 = 235
▣ Shortcut 3: Finding the Whole from a Percentage
If x% of a number = y, then the number = (y/x) × 100
Example 5
Problem: 20% of a number is 30. Find the number.
⚡ Shortcut:
Number = (30/20) × 100 = 1.5 × 100 = 150
▣ Shortcut 4: "More Than / Less Than" Ratio (Exam Favorite)
These are the most commonly asked percentage questions in banking and SSC exams.
Formula 4A: A is R% more than B
B is [R/(100+R) × 100]% less than A
Formula 4B: A is R% less than B
B is [R/(100−R) × 100]% more than A
Example 6 (Bank Exam Question)
Problem: Ram's salary is 30% more than Renu's. By what percent is Renu's salary less than Ram's?
Apply Formula 4A (R = 30):
= 30/(100+30) × 100
= 30/130 × 100
= 3000/130 ≈ 23.07%
Answer: 23.07%
Example 7
Problem: A's salary is 20% less than B's. By what percent is B's salary more than A's?
Apply Formula 4B (R = 20):
= 20/(100−20) × 100
= 20/80 × 100 = 25%
Answer: 25%
▣ Shortcut 5: Successive Percentage Change
⚠️ Warning:
Never add percentages directly for successive changes!
Net change = a + b + (a × b)/100
Use + for increase, – for decrease
Example 8
Problem: Price increases by 10%, then decreases by 10%. Net change?
Net = 10 + (−10) + (10 × −10)/100
= 0 + (−100)/100 = −1%
Answer: 1% decrease (not zero!)
Example 9
Problem: Salary increased by 20%, then another 10%. Net increase?
Net = 20 + 10 + (20 × 10)/100
= 30 + 2 = 32%
Answer: 32% increase
▣ Shortcut 6: Expenditure Constancy (Price ↑ → Consumption ↓)
Scenario: Price changes, but total expenditure remains the same.
Price increases by R%
Consumption drop = [R/(100+R) × 100]%
Price decreases by R%
Consumption increase = [R/(100−R) × 100]%
Example 10
Problem: Petrol price rises by 25%. By what percent must consumption reduce to keep bill unchanged?
Reduction = 25/(100+25) × 100
= 25/125 × 100 = 20%
Answer: 20% reduction
▣ Shortcut 7: Population Growth (Compound Interest Style)
Population after n years = P × (1 + R/100)n
- P = Present population
- R = Annual growth rate (%)
- n = Number of years
Example
Problem: A town's population is 20,000. It grows at 5% per year. Population after 2 years?
Year 1: 20,000 × 1.05 = 21,000
Year 2: 21,000 × 1.05 = 22,050
Answer: 22,050
▣ Shortcut 8: Depreciation (Value Decrease)
Value after n years = P × (1 − R/100)n
- P = Present value
- R = Annual depreciation rate (%)
- n = Number of years
Example
Problem: A machine worth ₹1,00,000 depreciates 10% yearly. Value after 2 years?
Year 1: 1,00,000 × 0.90 = 90,000
Year 2: 90,000 × 0.90 = 81,000
Answer: ₹81,000
▣ Shortcut 9: Passing Marks Problems
Scenario: Two students score different percentages. One fails by X marks, the other passes with Y extra marks.
Total Marks = [(X + Y) × 100] / (Q − P)
- P = First student's percentage
- Q = Second student's percentage
- X = Marks first student fell short by
- Y = Marks second student exceeded by
Example
Problem: A scores 30% and fails by 15 marks. B scores 40% and gets 35 marks above passing. Find total marks.
Total = [(15 + 35) × 100] / (40 − 30)
= (50 × 100) / 10 = 500
Answer: 500
▣ Shortcut 10: Election / Voting Percentage
Scenario: Total votes = Valid votes + Invalid votes. Two candidates contest.
Step-by-step method:
- Find the percentage difference between the two candidates
- That percentage of valid votes = Winning margin in votes
- Calculate valid votes, then total votes
Example
Problem: In an election, 10% votes were invalid. Winner got 60% of valid votes and won by 1800 votes. Find total voters.
Loser got = 40% of valid votes
Difference = 60% − 40% = 20%
20% of valid votes = 1800
Valid votes = 1800 × 5 = 9000
Total votes = 9000 × 100/90 = 10,000
Answer: 10,000
▣ Bonus: Quick Reference Card (Save This!)
| Problem Type | Shortcut Formula |
|---|---|
| x% of y | y% of x |
| Net % change (a, b) | a + b + (a×b)/100 |
| A is R% > B | B is [R/(100+R) × 100]% < A |
| A is R% < B | B is [R/(100−R) × 100]% > A |
| Price ↑ R%, keep expense same | Consumption ↓ [R/(100+R) × 100]% |
| Price ↓ R%, keep expense same | Consumption ↑ [R/(100−R) × 100]% |
| Population growth (n years) | P × (1 + R/100)n |
| Depreciation (n years) | P × (1 − R/100)n |
| Passing marks (two students) | [(X+Y) × 100] / (Q−P) |
▣ Practice Questions (Test Yourself)
Solve these using the shortcuts above.
| Q# | Question | Your Answer |
|---|---|---|
| 1 | What is 15% of 80? (Use swapping) | ______ |
| 2 | Find 37% of 200. (Use split method) | ______ |
| 3 | A's salary is 40% more than B's. B's salary is what percent less than A's? | ______ |
| 4 | Price increases by 20%, then 10%. Net change? | ______ |
| 5 | Petrol price rises 40%. By what percent must consumption drop? | ______ |
Answers
| Q# | Answer | Shortcut Used |
|---|---|---|
| 1 | 12 | Swapping: 80% of 15 = 12 |
| 2 | 74 | Split: 37% = 25% + 12% = 50 + 24 |
| 3 | 28.57% | More/Less formula: 40/140 × 100 |
| 4 | 32% increase | Successive change: 20 + 10 + 200/100 |
| 5 | 28.57% | Expenditure constancy: 40/140 × 100 |
▣ Final Words
Master these percentage shortcut tricks for aptitude tests, and you will:
- Solve problems 3x faster
- Reduce calculation errors
- Gain confidence in the quantitative section
Your next step:
Practice percentage questions daily for one week. Then watch your mock test scores rise.
Good luck! 🚀
▣ Frequently Asked Questions
Q: How many shortcut tricks should I memorize?
Focus on the 5 most important: Swapping, Split Method, Successive Change, More/Less Ratio, and Expenditure Constancy.
Q: Can I use these for SSC CGL and Bank exams?
Absolutely. These are standard percentage short tricks for competitive exams.
Q: Is there a PDF of these tricks?
You can save this page as PDF (Ctrl + P → Save as PDF) for offline practice.
Q: Do these work for decimal percentages like 6.5%?
Yes. Use the split method: 6.5% = 5% + 1.5% (or 1% + 0.5%).
🏁 Master Percentages, Master Your Exam
These 10 percentage shortcuts are your weapon for any competitive exam. Practice them daily, and you'll see your speed and accuracy skyrocket.
Remember:
Speed comes from practice, not from reading. Use this guide as your reference, but spend 70% of your preparation time actually solving problems.
Good luck with your exam preparation! 🚀
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