Solve the Addition Equation: Finding the Missing Number in 24 + □ = 45

Addition Equations with Two-Jump Strategy

Solve the addition exercise,

using two jumps on the number line below:

24+=45 24+\Box=45

242424454545

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Step-by-step written solution

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1

Understand the problem

Solve the addition exercise,

using two jumps on the number line below:

24+=45 24+\Box=45

242424454545

2

Step-by-step solution

To solve the equation 24+=45 24 + \Box = 45 using two jumps on a number line, we will take the following approach:

  • Step 1: Make the first jump from 24 to the closest higher round number, which is 30.
  • Step 2: Calculate how much is needed to reach from 30 to 45.
  • Finally, we combine the lengths of the two jumps to find \Box .

Now, let's calculate each step:

Step 1: The first jump from 24 to 30 is 6 units.

Step 2: From 30 to 45, the jump is 15 units.

Adding these two jumps: 6+15=21 6 + 15 = 21 .

Therefore, the number that completes the equation 24+=45 24 + \Box = 45 is 21 21 .

3

Final Answer

21 21

Key Points to Remember

Essential concepts to master this topic
  • Missing addend rule: To find the missing number, subtract the known addend from the sum
  • Two-jump technique: First jump from 24 to 30 (6 units), then 30 to 45 (15 units)
  • Verification: Check that 24 + 21 = 45 and 6 + 15 = 21 ✓

Common Mistakes

Avoid these frequent errors
  • Adding jumps incorrectly or skipping verification
    Don't just guess numbers without calculating the jumps = wrong answer like 20 or 23! Students often miscount the distance between numbers. Always break into clear steps: find each jump distance, add them together, then verify with the original equation.

Practice Quiz

Test your knowledge with interactive questions

If we have 67 blocks in total, how many blocks will remain if we remove 5 tens and 4 ones?

FAQ

Everything you need to know about this question

Why do we need to use exactly two jumps on the number line?

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Using two jumps makes large differences easier to calculate! Instead of counting from 24 to 45 one by one, we jump to a round number (like 30) first, then complete the journey.

How do I choose where to make my first jump?

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Jump to the nearest round number that's higher than your starting point. From 24, the closest round number is 30, making the first jump easy to calculate (24 + 6 = 30).

What if I get different numbers for my two jumps?

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That's normal! The jumps don't have to be equal. Just make sure each jump calculation is correct:

  • First jump: 24 to 30 = 6 units
  • Second jump: 30 to 45 = 15 units
  • Total: 6 + 15 = 21

How can I check if my answer is right?

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Use substitution! Replace the box with your answer: 24+21=45 24 + 21 = 45 . If both sides equal the same number, you're correct!

Can I use this method for any addition equation?

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Yes! The two-jump strategy works especially well when you have larger numbers. Always jump to round numbers (like 10, 20, 30) to make calculations easier.

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