Why Percentage Shortcuts Matter for SSC CGL Tier 1
Ever felt the clock ticking while you’re stuck on a simple % question? In the SSC CGL Tier 1 exam, every second counts, and a quick shortcut can be the difference between a right answer and a blank.
💡 In Simple Words: A percentage shortcut is a mental trick that lets you find a % of a number faster than using the usual formula. Think of it like a shortcut on a video game – you reach the goal with fewer steps.
Basic Idea Behind Percentage Shortcuts
Normally you’d multiply the number by the percentage and then divide by 100. That works, but it also wastes time. The shortcut method rewrites the same calculation into easier mental steps, like breaking 18% into 10% + 5% + 2% and adding the parts.
Common Quick Tricks
- 10% = divide by 10. Easy as cutting a pizza into ten equal slices.
- 5% = half of 10%. If 10% of 80 is 8, then 5% is 4.
- 20% = double 10%. Double the 10% slice.
- 25% = quarter of the whole. Think of splitting a chocolate bar into four equal parts.
- 1% = move decimal left two places. 350 becomes 3.5.
Worked Examples
Example 1: Find 18% of 250.
Step 1: 10% of 250 = 25 (just shift the decimal).
Step 2: 5% of 250 = half of 25 = 12.5.
Step 3: 2% of 250 = 1% of 250 twice = 2.5 + 2.5 = 5.
Step 4: Add them: 25 + 12.5 + 5 = 42.5.
Instead of multiplying 250 × 0.18, you did three tiny mental jumps.
Example 2: What is 35% of 480?
Break 35% into 30% + 5%.
30% = 3 × 10% → 3 × 48 = 144.
5% = half of 10% → half of 48 = 24.
Result: 144 + 24 = 168.
Example 3: Calculate 7% of 1,200.
7% = 5% + 2%.
5% = half of 10% → half of 120 = 60.
2% = 1% twice → 12 + 12 = 24.
Total = 60 + 24 = 84.
How to Apply a Percentage Shortcut
Quick Reference Table
| Percentage | Shortcut | How to use |
|---|---|---|
| 1% | Move decimal left two places | 350 → 3.5 |
| 5% | Half of 10% | 10% of 80 = 8 → 5% = 4 |
| 10% | Divide by 10 | 250 → 25 |
| 20% | Double 10% | 10% of 90 = 9 → 20% = 18 |
| 25% | Quarter of the whole | 100 → 25 |
| 50% | Half of the number | 84 → 42 |
📝 Likely Exam Questions
- Find 12% of 475.
Answer: 10% = 47.5, 2% = 9.5, total = 57. - A shop offers a 15% discount on a TV priced at ₹12,800. What is the discounted price?
Answer: 10% = 1,280; 5% = 640; discount = 1,920; price = 12,800 – 1,920 = ₹10,880. - If a bank gives a 7.5% annual interest on ₹20,000, how much interest is earned in one year?
Answer: 5% = 1,000; 2% = 400; 0.5% = 100; total = 1,500. - Calculate 33% of 150.
Answer: 30% = 45 (3 × 10% = 3 × 15); 3% = 4.5; total = 49.5. - A candidate scored 68% in a test of 250 marks. How many marks did he obtain?
Answer: 50% = 125; 10% = 25; 5% = 12.5; 3% = 7.5; add = 125+25+12.5+7.5 = 170 marks.