Approximation
SSC GD Self-Paced Course
1. What is Approximation?
Approximation means finding a value close to the exact value, which is good enough for practical purposes or for quick mental calculations.
Exam Context:
In exams like SSC, Delhi Police, or Banking, approximation helps you
solve questions faster when an exact answer is not required.
Exact Value: 24.97
→ Approximation: 25
Exact Value: 49.8 × 2.02
→ Approximation: 50 × 2 = 100
2. Why Approximation is Important?
Saves time in arithmetic questions
Helps eliminate wrong options in MCQs
Useful in percentage, ratio, and simplification problems
Example
If the exact value is 24.97, you can approximate it to 25 for quick calculation.
3. Rounding Off Rules
| Number | Digit after Decimal | Rounded Value |
|---|---|---|
| 23.1 | 1 < 5 | 23 |
| 46.6 | 6 ≥ 5 | 47 |
| 78.45 | 4 < 5 | 78 |
| 92.55 | 5 ≥ 5 | 93 |
Rounding Rule
If the digit after the rounding place is:
Less than 5 → Drop it
5 or more → Add 1 to the previous digit
4. Common Approximations to Remember
| Actual Value | Approximate Value |
|---|---|
| √2 | 1.4 |
| √3 | 1.7 |
| √5 | 2.2 |
| π (Pi) | 3.14 |
| 1/3 | 0.33 |
| 2/3 | 0.67 |
| 1/6 | 0.17 |
| 1/7 | 0.14 |
5. How to Use Approximation in Exams
Example 1
Find approximate value of:
49.7 × 2.05
≈ 50 × 2 = 100
Example 2
Find approximate value of:
(199 + 302) ÷ 5.1
≈ (500 ÷ 5) = 100
6. When to Use Approximation
✅ Use When
- • Question says "approximately", "nearly", "about"
- • Options are far apart (e.g., 100, 150, 200, 250)
- • Need quick mental calculation
❌ Don't Use When
- • Options are very close (e.g., 99.5, 100, 100.5)
- • Exact calculation is required
- • Dealing with precise measurements
7. Quick Recap
| Concept | Summary |
|---|---|
| Approximation | Estimating a close value |
| Usefulness | Saves time in MCQs |
| Rounding Rule | 5 or more → add 1 |
| Common Roots | √2 = 1.4, √3 = 1.7 |
| Tip | Use when options are far apart |
8. Practice Questions
Test your approximation skills with these practice questions. Click on "View Answer" to check your understanding.
Q1. Approximate value of 49.8 × 2.02 = ?
View Answer
50 × 2 = 100 ✅
Q2. (198 + 302) ÷ 4.9 = ?
View Answer
≈ 500 ÷ 5 = 100 ✅
Q3. 19.9 × 5.1 = ?
View Answer
≈ 20 × 5 = 100 ✅
Q4. √50 ≈ ?
View Answer
≈ √49 = 7 ✅
Q5. 98.7 ÷ 4.9 ≈ ?
View Answer
≈ 100 ÷ 5 = 20 ✅
Q6. (59.8 + 40.3) ≈ ?
View Answer
≈ 60 + 40 = 100 ✅
Q7. (101 × 49.9) ≈ ?
View Answer
≈ 100 × 50 = 5000 ✅
Q8. (24.8 + 75.2) ÷ 10 ≈ ?
View Answer
≈ 100 ÷ 10 = 10 ✅
Q9. (199 ÷ 9.8) ≈ ?
View Answer
≈ 200 ÷ 10 = 20 ✅
Q10. (15.8 × 3.9) ≈ ?
View Answer
≈ 16 × 4 = 64 ✅
Q11. (5.8 + 4.2) × 10 ≈ ?
View Answer
≈ 10 × 10 = 100 ✅
Q12. (499 ÷ 5) ≈ ?
View Answer
≈ 500 ÷ 5 = 100 ✅
Q13. (9.7)² ≈ ?
View Answer
≈ 10² = 100 ✅
Q14. (3.1 × 4.9) ≈ ?
View Answer
≈ 3 × 5 = 15 ✅
Q15. (7.9 × 8.1) ≈ ?
View Answer
≈ 8 × 8 = 64 ✅
✅ Exam Strategy Tip
🟢 Always check the options first - if they're far apart, use approximation
🟢 Round numbers to the nearest multiple of 5 or 10 for quick calculation
🟢 Memorize common square roots and fractions for instant approximation
🟢 Practice mental math to improve approximation speed
You've completed Approximation Concepts!
Courage Tip: Approximation is a powerful time-saving technique in competitive exams. Practice rounding numbers to the nearest convenient values and remember common approximations like square roots and fractions. The key is to balance accuracy with speed - use approximation when the options are sufficiently far apart, but be ready to calculate exactly when precision is needed. Regular practice will help you develop intuition for when and how much to approximate.
Master Approximation for Competitive Exams!
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