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🔢 Grade 3 • 🔟 Rounding to the Nearest 10 and 100

Rounding to the Nearest 10 and 100 for Grade 3

📖 Lesson Grade 3 Last updated: March 2026

Rounding helps students name a number that is close to the exact value. In Grade 3, rounding is used to estimate and to think about numbers flexibly.

What Rounding Means

When students round, they decide which benchmark number a value is closest to. For nearest ten, the benchmarks are multiples of 10. For nearest hundred, the benchmarks are multiples of 100.

Rounding does not change the exact number. It gives a nearby number that is easier to think about.

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Example 34 rounds to 30 because it is closer to 30 than to 40.

Round to the Nearest Ten

To round to the nearest ten, students look at the ones digit. If the ones digit is 0 to 4, round down. If it is 5 to 9, round up.

A number line helps show why this works. The midpoint between 30 and 40 is 35, so 35 and larger numbers go up to 40.

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Example 67 rounds to 70 because the ones digit is 7.
💡
Tip Place the number between two tens on a number line before saying the rounded answer.

Round to the Nearest Hundred

To round to the nearest hundred, students look at the tens digit. If the last two digits are less than 50, round down. If they are 50 or more, round up.

Students should picture the number between two hundreds and decide which hundred is closer.

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Example 372 rounds to 400 because it is closer to 400 than to 300.

Use Rounding to Estimate

Rounding is helpful when an exact answer is not needed right away. If a school has 198 books in one room, students can estimate that there are about 200 books.

Estimation helps students check whether exact answers are reasonable too.

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Example 451 rounds to 500, so about 500 people attended.

📝 Key Vocabulary

Rounding
Finding a nearby number that is easier to use
Estimate
A close answer, not an exact one
Place value
The value of a digit based on its place in a number

📐 Standards Alignment

3.NBT.A.1 CCSS.MATH

Use place value understanding to round whole numbers to the nearest 10 or 100.

MP7 CCSS.MATH

Look for and make use of structure.

🔗 Glossary Connections

Rounding Rounding means changing a number to a close number like the nearest ten or hundred. Estimate An estimate is a close answer, not the exact answer. Nearest Ten The nearest ten is the ten a number is closest to. Nearest Hundred The nearest hundred is the hundred a number is closest to. Place Value Place value tells us what a digit is worth because of where it is in the number.

⚠️ Common Mistakes to Watch For

  • Rounding to the wrong place value
  • Looking at the wrong digit before rounding
  • Treating the rounded number as the exact answer
🌍
Real-World Connection People round when they estimate crowd sizes, travel distances, prices, and how many supplies are needed.
🤩
Fun Fact! Scientists and engineers estimate with rounding all the time before checking exact values in more detail.