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Grade 2/Addition

Adding whole tens (3 addends, missing)

Find the missing whole tens addend in 3‑addend sums.
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Easy(Three tens to 50, find missing)
1
20 questions
2
20 questions
3
20 questions
4
20 questions
Medium(Three tens to 90, find missing)
1
20 questions
2
20 questions
3
20 questions
4
20 questions
Hard(Three tens 40–90, find missing)
1
20 questions
2
20 questions
3
20 questions
4
20 questions
Prerequisites
Adding whole tens (3 addends)12 WS
30 + 80 + 10 = ____
What to Do Next
Adding whole tens (4 addends)12 WS
30 + 80 + 10 + 20 = ____

Practice Questions

  1. 30 + ? + 10 = 120
    Show answer

    80

  2. 40 + ? + 20 = 100
    Show answer

    40

  3. 50 + ? + 30 = 110
    Show answer

    30

  4. 20 + ? + 40 = 100
    Show answer

    40

  5. 70 + ? + 10 = 120
    Show answer

    40

Teacher Resources
Teaching Notes

This challenges students to work backwards. Strategy: Add the two known numbers first, then subtract from the total. Example: "I know 30 + 40 = 70, and I need 100, so the missing number is 100 - 70 = 30." Encourage students to check their answer by adding all three numbers.

Vocabulary
Addend: A number used in addition.
Missing addend: An unknown number in an addition problem.
Common Mistakes
  • Subtracting in wrong order
  • Adding the two known numbers and stopping
  • Forgetting to check the answer
  • Confusing which number is missing
  • Forgetting to add the two known addends together before subtracting from the sum.
  • Errors in basic addition or subtraction of whole tens.
  • Misunderstanding the concept of a missing addend.
Differentiation
SupportUse base ten blocks or a number line to visually represent the whole tens. Start with problems involving only two addends before moving to three.
ChallengeIntroduce word problems involving missing whole tens. Challenge students with larger whole tens sums (e.g., up to 200 or 300) or problems with more than three addends.
Discussion Questions
  • What strategies can you use to add whole tens quickly?
  • How does knowing about subtraction help you find the missing number in an addition problem?
  • Can you explain your strategy for finding the missing whole ten to a partner?
Extension Activities
  • Use a number line to find differences.
  • Create equations with missing addends.
  • Play 'find the missing piece'.
Parent Tip

Give your child a total and two numbers; ask them to find the missing number.

Learning Path
Skill Cluster

Number Sense & Algebraic Thinking

Estimated Time

15 minutes

Skills Practiced
Missing addend tensSubtraction from totalMulti addend missing