Rounding Numbers Lesson: Definition, Examples & More

Lesson Overview

• What Does Rounding Mean?
• When to Round Up or Down
• Rounding to the Nearest Ten
• Rounding to the Nearest Hundred
• Identifying the Rounding Digit
• Understanding Rounding Boundaries
• More Practice with Nearest Ten
• More Practice with Nearest Hundred
• Why Do We Round Numbers?
• Applying Rounding in Math Problems

In math, we often deal with numbers that are long or tricky to work with. Wouldn't it be nice to simplify those numbers just a little? That's exactly what rounding helps us do. It makes numbers easier to work with, especially when solving problems quickly or estimating answers.

In this lesson, you'll learn:

• What rounding means and why we use it
  
• How to round numbers to the nearest ten and nearest hundred
  
• How to know when to round up or down
  
• Step-by-step strategies and examples
  
• How to use rounding to check answers and estimate
  

What Does Rounding Mean?

Rounding means changing a number to a nearby value that's simpler, but still close to the original number. This is helpful when:

• You don't need an exact number
  
• You want to estimate or do mental math
  
• You want to make calculations easier
  

Rounding doesn't give the exact number-it gives a close and friendly number.

When to Round Up or Down

To decide whether to round a number up or down, look at the digit to the right of the place you're rounding to.

🔹 The Rounding Rule:

• If the digit is 5 or more, round up
  
• If the digit is 4 or less, round down
  

This rule works whether you're rounding to the nearest ten, hundred, or even thousand.

Rounding to the Nearest Ten

To round to the nearest ten:

1. Look at the ones digit
   
2. Use the rounding rule (5 or more → up, 4 or less → down)
   
3. Replace the ones digit with 0
   

Example 1: Round 253 to the nearest ten

• Ones digit is 3 → round down
  
• The tens digit stays the same → 250
  Answer: 250​
  

Example 2: Round 781 to the nearest ten

• Ones digit is 1 → round down
  
• 781 becomes 780​
  

Example 3: Round 297 to the nearest ten

• Ones digit = 7 → round up
  
• 297 becomes 300
  

Rounding to the nearest ten makes it easier to add or subtract numbers quickly in your head.

Rounding to the Nearest Hundred

To round to the nearest hundred:

1. Look at the tens digit
   
2. Follow the rounding rule
   
3. Change both tens and ones digits to zeros
   

Example 1: Round 817 to the nearest hundred

• Tens digit = 1 → round down
  
• 817 becomes 800​
  

Example 2: Round 296 to the nearest hundred

• Tens digit = 9 → round up
  
• 296 becomes 300​
  

Example 3: Round 349 to the nearest hundred

• Tens digit = 4 → round down
  
• 349 becomes 300
  

The number always rounds to the nearest hundred mark, like 100, 200, 300...

Take This Quiz:

rounding to tens and hundreds quiz

Identifying the Rounding Digit

To round correctly, you must know which digit to look at:

Example:

Round 462 to the nearest ten

• Look at the ones digit: 2
  
• 2 is less than 5 → round down
  
• Tens place stays 6 → final answer = 460
  

So the digit you need to look at is 2​

Understanding Rounding Boundaries

Every number lies between two rounding points.

Example:

253 lies between:

• 250 (lower ten) and 260 (higher ten)
  Since the ones digit is 3 → round down → 250
  

817 lies between:

• 800 and 900
  Tens digit = 1 → round down → 800
  

When rounding, always ask: "What two tens or hundreds does this number fall between?"

More Practice with Nearest Ten

Example:

Round 174 to the nearest ten

• Ones digit = 4 → round down
  
• Answer = 170
  

Example:

Round 489 to the nearest ten

• Ones digit = 9 → round up
  
• 489 becomes 490
  

Example:

Round 305 to the nearest ten

• Ones digit = 5 → round up
  
• 305 becomes 310
  

If a number ends in 5, always round up.

Take This Quiz:

Quiz : How Well Do You Know About Rounding Numbers?

More Practice with Nearest Hundred

Example:

Round 722 to the nearest hundred

• Tens digit = 2 → round down
  
• Answer = 700
  

Example:

Round 685 to the nearest hundred

• Tens digit = 8 → round up
  
• 685 becomes 700
  

Example:

Round 150 to the nearest hundred

• Tens digit = 5 → round up
  
• Answer = 200
  

Use this rule:

• 0–4 → stay at current hundred
  
• 5–9 → go to next hundred
  

Why Do We Round Numbers?

We round numbers to:

• Estimate answers quickly
  
• Make numbers easier to work with
  
• Solve problems when we don't need exact amounts
  

Examples:

• Instead of 298 + 653, you can round to 300 + 650 = 950
  
• If something costs $47, you can round to $50 to estimate
  

Rounding is not always exact, but it is close enough for quick thinking and estimation.

Applying Rounding in Math Problems

You may be asked to round numbers as part of a bigger problem.

Example:

Your school collected 296 cans of food. Round this to the nearest hundred.

• Tens digit = 9 → round up
  
• Answer = 300
  

Example:

You walked 817 steps. Round this to the nearest hundred.

• Tens digit = 1 → round down
  
• Answer = 800
  

Rounding helps us estimate totals, plan better, and solve faster.