What your child learns
- Find the two tens or the two hundreds a number sits between.
- Decide which one the number is closer to, using a number line.
- Use the digit to the right of the rounding place: 0–4 rounds down, 5–9 rounds up.
- Use rounding to estimate and check answers.
Common Core 3.NBT.A.1
Rounding means replacing a number with a nearby "friendly" number that is easier to work with. In 3rd grade, children round to the nearest 10 and the nearest 100. The goal is not just to follow a rule but to understand closeness: 68 is nearer to 70 than to 60, so 68 rounds to 70.
Step 1: Find the "between" numbers
To round 68 to the nearest ten, ask: which two tens is 68 between? It is between 60 and 70. Halfway between them is 65.
Example 1: Round 68 to the nearest 10
- 68 is between 60 and 70.
- The halfway point is 65.
- 68 is past 65, so it is closer to 70.
- 68 rounds to 70.
Rule check: the ones digit is 8, which is 5 or more, so round up.
Step 2: Round to the nearest hundred
Rounding to the nearest hundred works the same way, but now the "between" numbers are hundreds and the digit to check is the tens digit.
Example 2: Round 432 to the nearest 100
- 432 is between 400 and 500. Halfway is 450.
- 432 is before 450, so it is closer to 400.
- The tens digit is 3, which is less than 5, so round down.
- 432 rounds to 400.
Example 3: The tricky one, 96 to the nearest 10
- 96 is between 90 and 100.
- The ones digit is 6, so round up.
- Rounding up from 90 gives the next ten, which is 100, not "910" or "90".
Numbers near the next hundred (95–99) are where most rounding mistakes happen. Drawing the number line makes the answer obvious.
Using rounding to estimate
Example 4: Is 287 + 412 about 700?
Round each number to the nearest hundred: 287 → 300 and 412 → 400. Then 300 + 400 = 700. The exact answer, 699, is very close, so it is reasonable.
Practice
- Round 43 to the nearest 10.
- Round 75 to the nearest 10.
- Round 128 to the nearest 10.
- Round 98 to the nearest 10.
- Round 361 to the nearest 100.
- Round 650 to the nearest 100.
- Round 949 to the nearest 100.
- A school has 518 students. About how many is that, to the nearest hundred?
- Estimate 192 + 304 by rounding to the nearest hundred.
Show answers
- 40
- 80
- 130
- 100
- 400
- 700
- 900
- About 500 students
- 200 + 300 = 500
Common mistakes and quick fixes
- Looking at the wrong digit: underline the rounding place, then circle the digit just to its right. Only that circled digit decides.
- Changing digits on the left: 361 to the nearest hundred is 400, not 461. Everything to the right of the rounding place becomes zero.
- Rounding 5 down: remind your child that exactly halfway always rounds up.
Try it at home
At the grocery store, round each price to the nearest dollar and add them in your head. Compare your estimate with the receipt total. How close did you get?
This guide matches Unit 1: Place Value and Rounding to 1,000 in Level Up Math, Grade 3 (coming January 2027). See all Grades 3–5 lessons.
Questions parents ask
What is the rule for rounding a 5?
When the digit you look at is exactly 5, round up. So 45 rounds to 50 and 350 rounds to 400.
Why learn rounding with a number line instead of just the rule?
The number line shows why the rule works: you are finding which ten or hundred the number is closer to. Children who see this make fewer mistakes with numbers like 95 or 999.
When will my child use rounding?
Rounding is the base of estimation, which children use to check whether an addition, subtraction or multiplication answer is reasonable.
