Rounding
Round to nearest 10, 100, and 1000; estimate sums.
Rounding
Rounding Numbers
What you'll learn
- Round numbers to the nearest 10, 100, and 1,000.
- Use the 5-or-more rule (look at the digit to the right).
- Estimate sums and differences for quick mental checks at the market.
Key concepts
Level 1 — Nearest ten
Look at the ones digit:
- 0–4 → round down (keep tens)
- 5–9 → round up (tens + 1)
| Number | Ones digit | Nearest ten |
|---|---|---|
| 847 | 7 | 850 |
| 842 | 2 | 840 |
| 845 | 5 | 850 |
Level 2 — Nearest hundred
Look at the tens digit:
| Number | Tens digit | Nearest hundred |
|---|---|---|
| 2,638 | 3 | 2,600 |
| 2,678 | 7 | 2,700 |
| 2,650 | 5 | 2,700 |
Level 3 — Nearest thousand
Look at the hundreds digit:
| Number | Hundreds digit | Nearest thousand |
|---|---|---|
| 4,499 | 4 | 4,000 |
| 4,500 | 5 | 5,000 |
| 7,850 | 8 | 8,000 |
Level 4 — Estimation in Indian context
At a Diwali mela, items cost ₹487, ₹312, and ₹205. Round each to nearest hundred: ₹500 + ₹300 + ₹200 ≈ ₹1,000 (exact sum = ₹1,004).
NCERT anchor: Math-Magic 4, Ch 1 — Building with Bricks; Ch 6 — The Junk Seller (estimating money and totals)
Worked example
Round 3,847 to the nearest hundred
Step 1 — Hundreds place is 8; look at tens digit **4**.
Step 2 — 4 < 5 → round down.
Step 3 — Replace tens and ones with 00.
Answer: **3,800**
Estimate total: ₹2,478 + ₹1,536 (nearest hundred)
Step 1 — 2,478 → **2,500**; 1,536 → **1,500**.
Step 2 — 2,500 + 1,500 = **4,000**.
Step 3 — Exact sum = 4,014 — estimate is close ✓
Common mistakes
| Mistake | Why it happens | Fix |
|---|---|---|
| Always rounding up when digit is 5 | Forgetting '5 rounds up' applies to the place left | 5 or more → round up; 4 or less → round down |
| Changing wrong digit (847 → 800 for nearest ten) | Looking at hundreds instead of ones | For nearest ten, check the ones digit only |
| 4,500 rounds to 4,000 (nearest thousand) | Stopping at 5 without checking hundreds=5 | Hundreds digit 5 → round up → 5,000 |
| Rounding and exact answer are always equal | Treating estimate as exact | Estimation is for quick checks — exact calculation still needed |
Quick check
- Round 2,456 to nearest ten, hundred, thousand.
- Round 5,050 to nearest hundred. (5,100)
- Estimate 3,892 + 1,107 to nearest thousand.
- Stretch: A cricket stadium has 8,475 seats. Round to nearest thousand for a newspaper headline. By how much does your rounded number differ from the exact count? (9,000; difference 525)
Revision tip: Underline the deciding digit in a different colour before you round — ones for tens, tens for hundreds, hundreds for thousands.
Open the Practice tab for graded questions on Rounding Numbers.
Key Takeaways (TL;DR)
- What you'll learn
- Key concepts
- Worked example
- Common mistakes
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