Rounding Numbers

Grade 3 Medium Number Sense & Place Value

Learning Objectives

  • Understand when and why we round numbers
  • Apply rounding rules to various place values

Concept Explanation

Rounding is a process of simplifying numbers by adjusting them to a nearby value that ends in one or more zeros. We round numbers to make them easier to work with, especially in estimation. The basic rule for rounding is: if the digit to the right of the rounding place is 5 or greater, round up; if it’s less than 5, round down.

Worked Examples

Example 1

Problem: Round 47 to the nearest ten.
Solution: 50
Explanation: The digit in the ones place is 7, which is greater than 5, so we round up to 50.

Example 2

Problem: Round 342 to the nearest hundred.
Solution: 300
Explanation: The digit in the tens place is 4, which is less than 5, so we round down to 300.

Example 3

Problem: Round 2,751 to the nearest thousand.
Solution: 3,000
Explanation: The digit in the hundreds place is 7, which is greater than 5, so we round up to 3,000.

Common Errors

ErrorCorrectionReason
Rounding in the wrong directionCheck if the critical digit is less than 5 or 5 and greaterStudents often round up when they should round down, or vice versa.
Looking at the wrong digitIdentify the place value you’re rounding to, then look at the digit to its rightWhen rounding to the nearest ten, look at the ones digit.
Changing only one digitAdjust all digits to the right of the rounding place to zerosWhen rounding 478 to the nearest hundred, the result is 500, not 400.

Practice Problems

  1. Problem: Round 63 to the nearest ten.
    Solution: 60
  2. Problem: Round 856 to the nearest hundred.
    Solution: 900
  3. Problem: Round 1,495 to the nearest thousand.
    Solution: 1,000
  4. Problem: Round 25 to the nearest ten.
    Solution: 30
  5. Problem: Round 750 to the nearest hundred.
    Solution: 800

Real-World Application Example

Rounding is used in many practical situations, such as estimating the cost of groceries, reporting approximate distances or times, or simplifying large numbers in news reports. For example, if you have 23.47inyourwallet,youmightroundto23.47 in your wallet, you might round to23 or 20toquicklyestimateifyouhaveenoughmoneyfora20 to quickly estimate if you have enough money for a15 purchase.

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