Rounding & Estimation — Grade 4 Mathematics
In Grade 4, we round 5-digit numbers to any place value and use rounding to estimate answers to multi-step calculations — an essential skill for checking our work.
Rounding Rules
To round a number, look at the digit immediately to the right of the rounding place:
• If it is 0–4: round down (leave the rounding digit unchanged, replace all digits to its right with 0).
• If it is 5–9: round up (add 1 to the rounding digit, replace all digits to its right with 0).
• If it is 0–4: round down (leave the rounding digit unchanged, replace all digits to its right with 0).
• If it is 5–9: round up (add 1 to the rounding digit, replace all digits to its right with 0).
| Number | To nearest 10 | To nearest 100 | To nearest 1 000 | To nearest 10 000 |
|---|---|---|---|---|
| 47 836 | 47 840 | 47 800 | 48 000 | 50 000 |
| 23 450 | 23 450 | 23 500 | 23 000 | 20 000 |
| 89 507 | 89 510 | 89 500 | 90 000 | 90 000 |
💡 Tip: For 23 450 rounded to the nearest 1 000 — the hundreds digit is 4, so we round down to 23 000.
Using Rounding to Estimate
Round each number first, then perform the calculation. The symbol ≈ means "approximately equal to".
Addition:
3 847 + 5 219
≈ 4 000 + 5 000 = 9 000
3 847 + 5 219
≈ 4 000 + 5 000 = 9 000
Multiplication:
48 × 63
≈ 50 × 60 = 3 000
48 × 63
≈ 50 × 60 = 3 000
Division:
7 193 ÷ 7
≈ 7 000 ÷ 7 = 1 000
7 193 ÷ 7
≈ 7 000 ÷ 7 = 1 000
Worked Examples
Example 1 — Round to Four Different Places
Round 63 478 to the nearest 10, 100, 1 000, and 10 000.
- Nearest 10: look at units digit 8 → 8 ≥ 5 → round up: 63 480
- Nearest 100: look at tens digit 7 → 7 ≥ 5 → round up: 63 500
- Nearest 1 000: look at hundreds digit 4 → 4 < 5 → round down: 63 000
- Nearest 10 000: look at thousands digit 3 → 3 < 5 → round down: 60 000
Example 2 — Estimate a Multi-Step Calculation
Estimate 4 816 × 7 + 2 039.
- Round 4 816 → 5 000; round 2 039 → 2 000
- 5 000 × 7 = 35 000
- 35 000 + 2 000 = ≈ 37 000
- Exact answer: 33 712 + 2 039 = 35 751 — our estimate is close! ✓
Example 3 — Is My Answer Reasonable? 🎯
A student says 327 × 48 = 2 080. Use estimation to check.
- 327 ≈ 300; 48 ≈ 50
- 300 × 50 = 15 000
- The estimate is 15 000 — far from 2 080, so the answer is wrong.
- Exact answer: 327 × 48 = 15 696 ✓
Practice Questions
1. Round 58 249 to the nearest 1 000.
✅ Hundreds digit is 2 (less than 5) → round down: 58 000
2. Round 72 651 to the nearest 10 000.
✅ Thousands digit is 2 (less than 5) → round down: 70 000
3. Estimate 6 234 + 3 879 by rounding to the nearest 1 000.
✅ 6 234 ≈ 6 000; 3 879 ≈ 4 000; estimate = 10 000 (exact: 10 113)
4. Estimate 493 × 22.
✅ 493 ≈ 500; 22 ≈ 20; estimate = 500 × 20 = 10 000 (exact: 10 846)
5. A student says 81 × 43 = 378. Use estimation to explain why this is wrong.
✅ 81 ≈ 80; 43 ≈ 40; estimate = 80 × 40 = 3 200. The answer 378 is far too small. Exact: 3 483.
Key Points to Remember
- Look at the digit to the right of the rounding place to decide up or down.
- 5 or more → round up; 4 or less → round down.
- Use ≈ to show an estimated (not exact) answer.
- Estimation is a powerful tool for checking whether an answer is reasonable.
- Larger place values give rougher estimates; smaller place values give more accurate ones.