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👩‍🏫 Teaching Guide • Grade 3

How to Teach Rounding to the Nearest 10 and 100

Rounding makes the most sense when students can see two benchmark numbers and decide which one is closer. This guide keeps rounding grounded in place value and estimation.

📐 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.

📦 Materials Needed

  • Open number lines
  • Place-value charts
  • Digit cards
  • Whiteboards

🎯 Teaching Strategies

💡
Use Benchmark Numbers Always place the number between the two tens or two hundreds it sits between before deciding how to round.
💡
Explain the Midpoint Show that 35 is the halfway point between 30 and 40, and 350 is the halfway point between 300 and 400.
💡
Connect Rounding to Estimation Ask students to round numbers in real situations so they see why close answers can be useful.

⚠️ Common Misconceptions

❌ Misconception: Students round by changing only the last digit

✅ Correction: Return to place value and ask which place is being rounded and what the benchmark numbers are.

❌ Misconception: Students think rounding changes the exact value

✅ Correction: Compare the exact number and the estimate side by side and discuss the difference.

📊 Differentiation Tips

Struggling

Stay with nearest ten on open number lines before moving to hundreds.

On-level

Mix standalone rounding practice with real-world estimation problems.

Advanced

Ask students to justify why a number is closer to one benchmark than the other.

🚀 Extension Activities

  1. Make a classroom rounding number line with sticky notes.
  2. Estimate counts of books, blocks, or pencils by rounding.
  3. Sort numbers into bins labeled round to 20, 30, 40, and so on.