Solve Addition Equation: Find Missing Number in 33 + □ = 42

Missing Addend with Number Line Jumps

Solve the addition exercise,

using two jumps on the number line below:

33+=42 33+\Box=42

333333424242

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the addition exercise,

using two jumps on the number line below:

33+=42 33+\Box=42

333333424242

2

Step-by-step solution

To solve the problem 33+=42 33 + \Box = 42 using the number line, we will make strategic jumps:

First, jump from 33 to the nearest higher round number, which is 40:

  • This first jump is 4033=7 40 - 33 = 7 .

Next, jump from 40 to 42:

  • This second jump is 4240=2 42 - 40 = 2 .

Add the two jumps to find \Box:

  • =7+2=9\Box = 7 + 2 = 9

Therefore, the solution to the problem is 9 9 .

3

Final Answer

9 9

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find missing addend by subtracting known values from sum
  • Technique: Jump from 33 to 40 (7 units) then 40 to 42 (2 units)
  • Check: Verify that 33 + 9 = 42 on the number line ✓

Common Mistakes

Avoid these frequent errors
  • Making one large jump instead of strategic smaller jumps
    Don't try to jump directly from 33 to 42 and count all units = difficult counting and errors! This makes it hard to see the relationship between numbers. Always break the jump into easier steps using round numbers like 40.

Practice Quiz

Test your knowledge with interactive questions

If we have 85 blocks in total, how many blocks will remain if we remove 4 tens and 1 one?

FAQ

Everything you need to know about this question

Why do I need to use two jumps instead of one?

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Using two strategic jumps makes counting easier! Jumping to round numbers like 40 first helps you break big problems into smaller, manageable steps.

What if I don't want to jump to 40 first?

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You could jump to other numbers, but round numbers like 40 make mental math much easier. Try different strategies and see which feels most comfortable!

How do I know which direction to jump on the number line?

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Since we're adding to 33 to get 42, we always move to the right (toward larger numbers) on the number line.

Can I solve this without a number line?

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Yes! You can use subtraction: 4233=9 42 - 33 = 9 . But the number line helps you visualize the problem and understand what addition really means.

What if my two jumps don't add up correctly?

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Double-check your counting! Make sure your first jump lands exactly on your chosen middle number, then count carefully for the second jump. Practice makes perfect!

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