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Fifth/Base 10 Blocks

✏️ Decompose the Number: Tens and Ones

Students look at a two-digit number and break it into its tens and ones parts. For example, 34 becomes 3 tens + 4 ones. This worksheet builds number sense and connects written numbers to the place value system — a key foundation for addition, subtraction, and mental math.
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What to Do Next
🔢 Compare Two Numbers: Tens and Ones6 WS
34 ___ 21

Practice Questions

  1. 13 = ? tens + ? ones
    Show answer

    1 ten + 3 ones

  2. 25 = ? tens + ? ones
    Show answer

    2 tens + 5 ones

  3. 30 = ? tens + ? ones
    Show answer

    3 tens + 0 ones

  4. 34 = ? tens + ? ones
    Show answer

    3 tens + 4 ones

Teacher Resources
Teaching Notes

This worksheet is the reverse of Count the Blocks — instead of seeing blocks and writing a number, students see a number and identify its parts.

Common Mistakes
  • Reversing the digits (writing 4 tens + 3 ones for the number 34)
  • Thinking the tens place shows the total value (e.g., writing 34 tens instead of 3 tens)
  • Struggling with round tens like 20 or 30 — remind them 0 ones is still valid
Differentiation
SupportGive students a place value chart to write the number in before filling in the blanks.
ChallengeAsk students to write the expanded form too: 34 = 30 + 4.
Discussion Questions
  • What do the two digits in a two-digit number each mean?
  • If a number has a 0 in the ones place, what does that tell you?
Extension Activities
  • Write 5 two-digit numbers, then decompose each one
  • Play partner quiz: one person says a number, the other writes the tens and ones
Learning Path
Skill Level

beginner

Estimated Time

12 minutes

Skills Practiced
Tens and ones decompose