This grade 3 rounding lesson explains rounding to the nearest 10 and 100 in one printable page, with definitions, a method and a worked example.
Rounding means replacing a number with a nearby number that ends in zero. To round to the nearest 10 or 100, find that place, look at the digit to its right, and round up if it is 5 or more or stay the same if it is 4 or less. A halfway number, like 45, rounds up.
Grade 3 Rounding Lesson: key facts
- Round to the nearest 10 by looking at the ones digit.
- Round to the nearest 100 by looking at the tens digit.
- A digit of 5 or more rounds up; a digit of 4 or less rounds down.
- Halfway numbers such as 45 and 450 round up.
- Rounded numbers help you estimate sums and differences.
What does it mean to round a number?
Rounding replaces a number with a nearby number that is easier to work with. The new number ends in zero. If a stadium sold 4,962 tickets, people say “about 5,000.” In third grade you round whole numbers to the nearest 10 or the nearest 100.
Think of a number line. Thirty-four sits between 30 and 40, and it is closer to 30. So 34 rounds to 30.
How do you round to the nearest 10?
- Find the tens place. Circle that digit.
- Look at the digit to its right, the ones digit.
- If the ones digit is 0, 1, 2, 3, or 4, keep the tens digit and change the ones digit to 0.
- If the ones digit is 5, 6, 7, 8, or 9, add 1 to the tens digit and change the ones digit to 0.
Example. Round 67 to the nearest 10. The tens digit is 6 and the ones digit is 7. Since 7 is 5 or more, the 6 becomes 7. So 67 rounds to 70.
What happens when the digit is exactly 5?
A number like 45 is exactly halfway between 40 and 50. Mathematicians agreed on one rule so everyone gets the same answer: halfway numbers round up. So 45 rounds to 50, and 135 rounds to 140.
How do you round to the nearest 100?
Use the same idea one place to the left. Circle the hundreds digit and look at the tens digit.
- Tens digit 0 to 4: the hundreds digit stays the same.
- Tens digit 5 to 9: add 1 to the hundreds digit.
Then write 0 in the tens and ones places. The halfway point between 400 and 500 is 450. Since 462 is past 450, it rounds to 500.
Now try 238. The halfway point between 200 and 300 is 250. Because 238 is less than 250, it rounds down to 200.
What if the digit is 9 and you add 1?
Sometimes adding 1 makes a new place. Round 98 to the nearest 10. The tens digit 9 goes up by 1, which makes 10 tens, or 100. So 98 rounds to 100. In the same way, 996 rounds to 1,000 when rounded to the nearest 10 or the nearest 100.
Why do people round?
Rounded numbers make quick estimates. To estimate 38 + 47, round to 40 + 50 = 90. The exact answer is 85, which is close to 90. An estimate tells you if an answer is reasonable.
| Number | Nearest 10 | Nearest 100 |
|---|---|---|
| 284 | 280 | 300 |
| 351 | 350 | 400 |
| 605 | 610 | 600 |
Rounding to the Nearest 10 and 100: frequently asked questions
What is rounding in third grade math?
Rounding changes a number to the nearest ten or hundred. The new number is easier to use in your head. For example, 83 rounds to 80 and 683 rounds to 700.
Does 5 round up or down?
A 5 rounds up. The number 35 is halfway between 30 and 40, and it rounds to 40. The number 250 rounds to 300 when you round to the nearest 100.
How do you round to the nearest 100?
Look at the tens digit. If it is 5 or more, add 1 to the hundreds digit. If it is 4 or less, keep the hundreds digit. Write zeros in the tens and ones places.
Why does 98 round to 100?
The tens digit 9 goes up by 1 and becomes 10 tens. Ten tens make 100. So 98 is closer to 100 than to 90.
When do you use rounding?
You round to estimate answers and check that they make sense. If you add 38 + 47, rounding gives 40 + 50 = 90, so an answer like 850 would be unreasonable.
How to use this grade 3 rounding lesson
Use this grade 3 rounding lesson before the worksheet, then check what you learned with the quiz.
See every chapter on the Grade 3 math page.
