Third/Base 10 Blocks
🟦 Decompose the Number: Hundreds, Tens, and Ones
Students break a three-digit number into hundreds, tens, and ones, writing each part in a fill-in-the-blank equation. This builds directly on physical Base 10 Blocks understanding and strengthens the expanded-form skills needed for multi-digit addition, subtraction, and rounding.
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Practice Questions
- 234 = ? hundreds + ? tens + ? ones
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2 hundreds + 3 tens + 4 ones
- 105 = ? hundreds + ? tens + ? ones
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1 hundred + 0 tens + 5 ones
- 380 = ? hundreds + ? tens + ? ones
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3 hundreds + 8 tens + 0 ones
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Teacher Resources
Teaching Notes
This is the GR2 extension of Decompose the Number (GR1, tens and ones). Pair with the Count the Blocks: Hundreds, Tens, and Ones collection — have students count blocks first, then decompose the same numbers without blocks.
Common Mistakes
- Writing the ones digit as the hundreds (reversing the order)
- Forgetting to write 0 for a missing place value (e.g. skipping the tens blank for 304)
- Adding the digits together instead of keeping their place value (writing 9 instead of 2+3+4=234)
Differentiation
SupportUse a place value chart with H, T, O columns. Write the number in the chart first, then transfer each digit to the blank.
ChallengeHave students write the full expanded form equation: 234 = 200 + 30 + 4.
Discussion Questions
- Why does the position of a digit matter in a number?
- What does it mean when a number has a 0 in the tens place?
- How is decomposing 234 similar to decomposing 34?
Extension Activities
- Decompose a number two different ways (e.g. 234 = 2 hundreds + 3 tens + 4 ones, or 1 hundred + 13 tens + 4 ones)
- Build the number with physical Base 10 blocks, then write the decomposition
- Write the expanded form (200 + 30 + 4) for five different numbers
Learning Path
Skill Level
intermediate
Estimated Time
15 minutes
Skills Practiced
Three digit decomposition