3rd Grade Rounding to the Nearest 10 and 100 Lesson (Free PDF)
This grade 3 rounding lesson for 3rd Grade covers rounding to the nearest 10 and 100 (Common Core 3.NBT.A.1), with a free PDF to print.
To round a whole number, find the closest multiple of 10 or 100. For the nearest 10, look at the ones digit. For the nearest 100, look at the tens digit. A digit of 5 or more rounds up, and a digit of 4 or less rounds down. A number line shows why this works.
Grade 3 · Common Core State Standards: 3.NBT.A.1
Key facts in this grade 3 rounding lesson
- Rounding to the nearest 10 depends on the ones digit.
- Rounding to the nearest 100 depends on the tens digit.
- A digit of 5 or more rounds up. A digit of 4 or less rounds down.
- A number exactly halfway rounds up, so 45 rounds to 50.
- Rounded numbers make quick estimates for sums and differences.
What does it mean to round a number?
Rounding swaps a number for a nearby friendly number. It is handy when you do not need the exact amount, such as when a sign says that about 500 fans came to a game.
How do you round to the nearest 10?
Picture the number on a number line. The number 47 sits between 40 and 50. The halfway point is 45. Because 47 is past the halfway point, it is closer to 50.
You can skip the number line with a quick rule. Look at the digit in the ones place.
- If the ones digit is 0, 1, 2, 3, or 4, the tens digit stays the same. Round down.
- If the ones digit is 5, 6, 7, 8, or 9, add 1 to the tens digit. Round up.
- Change the ones digit to 0.
For 683, the ones digit is 3, so the tens stay put: 683 rounds to 680 to the nearest ten.
How do you round to the nearest 100?
Now look at the digit in the tens place. The number 462 sits between 400 and 500. The halfway point is 450, and 462 is past it, so 462 rounds up to 500.
The same rule works. A tens digit of 0 to 4 rounds down. A tens digit of 5 to 9 rounds up. Then change the tens and ones digits to 0.
Which numbers round to the same ten?
All the numbers from 65 up to 74 round to 70. The number 65 is halfway, so it rounds up. The number 75 is the next halfway point, so it belongs to 80.
How does rounding help you estimate?
Round each number first, then add or subtract the easy numbers. For 187 + 214, round to the nearest hundred and add 200 + 200 = 400. The exact sum is 401, so the estimate is very close.
| Number | Nearest 10 | Nearest 100 |
|---|---|---|
| \(248\) | \(250\) | \(200\) |
| \(755\) | \(760\) | \(800\) |
| \(996\) | \(1{,}000\) | \(1{,}000\) |
Grade 3 rounding lesson: questions and answers
What is the rule for rounding to the nearest 10?
Look at the ones digit. If it is 4 or less, round down. If it is 5 or more, round up. Then write 0 in the ones place. For example, 83 rounds to 80 and 87 rounds to 90.
What do you do when the number is exactly halfway?
Round up. The number 45 is halfway between 40 and 50, so it rounds to 50. The number 250 is halfway between 200 and 300, so it rounds to 300.
Which digit do you look at to round to the nearest 100?
Look at the digit in the tens place. A tens digit of 5 or more rounds up, and 4 or less rounds down. Digits to the right of the tens place do not matter.
Why does 996 round to 1,000?
The tens digit is 9, so round up. The hundreds digit 9 becomes 10, which gives 1,000. Rounding to the nearest ten also gives 1,000 because 996 is closer to 1,000 than to 990.
How is rounding used to estimate?
Round each number to the same place, then add or subtract the rounded numbers. This gives a fast answer that is close to the exact one and helps you check for mistakes.
How to use this grade 3 rounding lesson
Read the definitions first, then follow the worked method line by line and redo the example on paper without looking. When every step makes sense, move on to the worksheet, then check yourself with the quiz.
Download the grade 3 rounding lesson as a PDF with the button below and keep it with your notes.
Download the grade 3 rounding lesson as a PDF with the button below and keep it with your notes.
All Grade 3 chapters: Grade 3 math.
