Rounding Numbers

Why Round Numbers?

Rounding makes numbers easier to work with by making them simpler.

Real-life examples:

• "About 30 students in class" instead of "27 students"
• "Around $50" instead of "$47.82"
• "Nearly 100 people" instead of "96 people"

Rounding Rules

The basic rule:

• If the digit you're looking at is 5 or more, round UP
• If the digit is 4 or less, round DOWN

Remember: "Five or more? Raise the score! Four or less? Let it rest!"

Rounding to the Nearest 10

Steps:

1. Find the ones place
2. Look at that digit
3. If it's 5 or more → round up
4. If it's 4 or less → round down
5. Replace the ones digit with 0

Examples:

• 27 → Look at 7 → 7 ≥ 5 → Round up → 30
• 43 → Look at 3 → 3 < 5 → Round down → 40
• 85 → Look at 5 → 5 = 5 → Round up → 90
• 92 → Look at 2 → 2 < 5 → Round down → 90

Rounding to the Nearest 100

Steps:

1. Find the tens place
2. Look at that digit
3. If it's 5 or more → round up
4. If it's 4 or less → round down
5. Replace tens and ones with 0

Examples:

• 347 → Look at 4 (tens) → 4 < 5 → Round down → 300
• 682 → Look at 8 (tens) → 8 ≥ 5 → Round up → 700
• 450 → Look at 5 (tens) → 5 = 5 → Round up → 500
• 199 → Look at 9 (tens) → 9 ≥ 5 → Round up → 200

Rounding to the Nearest 1,000

Steps:

1. Find the hundreds place
2. Look at that digit
3. Apply the rounding rule
4. Replace hundreds, tens, and ones with 0

Examples:

• 3,621 → Look at 6 (hundreds) → 6 ≥ 5 → Round up → 4,000
• 7,389 → Look at 3 (hundreds) → 3 < 5 → Round down → 7,000
• 5,500 → Look at 5 (hundreds) → 5 = 5 → Round up → 6,000

Using a Number Line

A number line helps you see which number is closer:

For 27:

20 ←―――27―――→ 30

27 is closer to 30, so round to 30 ✓

For 43:

40 ←―43――――→ 50

43 is closer to 40, so round to 40 ✓

Practice Strategy

Quick method:

1. Underline the place you're rounding to
2. Circle the digit to the right
3. Use the rule: 5+ up, 4- down
4. Change all digits to the right to zeros

Example: Round 3,678 to nearest hundred

• Underline: 3,678
• Circle: 3,678
• 7 ≥ 5, so round up
• Answer: 3,700

Common Mistakes

❌ Looking at the wrong digit ❌ Forgetting to change digits to the right to zero ❌ Rounding 5 down instead of up

✅ Always look ONE place to the right of where you're rounding ✅ Remember: 5 rounds UP ✅ Replace all digits to the right with zeros