Solve the Subtraction Equation: 3609 - □ = 9

Q: How can I remember which operation to use?

Use the inverse operation rule: subtraction and addition are opposites. If the problem shows subtraction, use addition to solve for the missing number. Write it as: missing number = starting number - result.

Q: What if I get confused about which number goes where?

Always identify the three parts first:Starting number: 3609Result: 9Missing subtrahend: what we need to findThen: Missing subtrahend = Starting number - Result

Q: How do I check if 3600 is really correct?

Substitute it back into the original equation: $ 3609 - 3600 = ? $. If you get 9, then 3600 is correct! This is called the substitution check.

Q: Is there a faster way to do this subtraction?

Yes! Notice that $ 3609 - 9 $ is like subtracting 9 from the ones place. Since 9 - 9 = 0, you get 3600. Mental math tip: when subtracting from the ones place, focus on that digit first!

Algebraic Reasoning with Missing Subtrahends

Complete the following equation:

$3609-\Box=9$

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Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

Complete the following equation:

$3609-\Box=9$

Step-by-step solution

To solve this subtraction problem, follow these steps:

Step 1: Identify the equation given in the problem: $3609 - \Box = 9$ .
Step 2: Recognize that $\Box$ is the number that needs to be subtracted from 3609 to result in 9.
Step 3: Rearrange the equation to isolate $\Box$ :

We use the subtraction property: $\Box = 3609 - 9$ .

Step 4: Perform the subtraction:

Calculate $3609 - 9 = 3600$ .

Step 5: Verify the calculation:

Double-check the subtraction to ensure accuracy: if 3600 is subtracted from 3609, the remainder is indeed 9.

Step 6: Review the choices to see which matches the calculated solution.

The correct choice is 3600, which is option 4.

Therefore, the solution to the problem is $\Box = 3600$ .

Final Answer

$3600$

Key Points to Remember

Essential concepts to master this topic

Inverse Operations: Use addition to find the missing subtrahend value
Rearrangement: Transform $3609 - \Box = 9$ into $\Box = 3609 - 9$
Verification: Check that $3609 - 3600 = 9$ matches the original equation ✓

Common Mistakes

Avoid these frequent errors

Adding instead of subtracting to find the missing value
Don't calculate 3609 + 9 = 3618! This gives the wrong answer because you're going in the wrong direction. Always remember: to find what was subtracted, subtract the result from the original number.

Practice Quiz

Test your knowledge with interactive questions

Choose the correct answer:

$693+705=\text{ ?}$

FAQ

Everything you need to know about this question

Why do I subtract 9 from 3609 instead of adding?

Think of it this way: if you started with 3609 and ended up with 9, you must have subtracted something. To find what was subtracted, you work backwards by subtracting the result (9) from the starting number (3609).

How can I remember which operation to use?

Use the inverse operation rule: subtraction and addition are opposites. If the problem shows subtraction, use addition to solve for the missing number. Write it as: missing number = starting number - result.

What if I get confused about which number goes where?

Always identify the three parts first:

Starting number: 3609
Result: 9
Missing subtrahend: what we need to find

Then: Missing subtrahend = Starting number - Result

How do I check if 3600 is really correct?

Substitute it back into the original equation: $3609 - 3600 = ?$ . If you get 9, then 3600 is correct! This is called the substitution check.

Is there a faster way to do this subtraction?

Yes! Notice that $3609 - 9$ is like subtracting 9 from the ones place. Since 9 - 9 = 0, you get 3600. Mental math tip: when subtracting from the ones place, focus on that digit first!

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