Solve the Equation: Finding the Missing Number in 1000 + □ = 1100

Q: Why do I subtract 1000 from 1100 instead of adding them?

Because we need to isolate the unknown! Think of it like this: if 1000 + something = 1100, then that 'something' must be the difference between 1100 and 1000.

Q: What if the missing number was in a different position?

The method stays the same! Whether it's $ \Box + 1000 = 1100 $ or $ 1000 + \Box = 1100 $, you still subtract the known addend from the sum to find the missing one.

Q: Is there a pattern with numbers ending in zeros?

Yes! When working with round numbers like 1000 and 1100, focus on the hundreds place. The difference is 1100 - 1000 = 100, which makes sense because 11 - 10 = 1 hundred.

Q: What if I picked 1000 as my answer by mistake?

Let's check: $ 1000 + 1000 = 2000 $, not 1100! Always verify your choice by substituting it back into the original equation.

Basic Addition Equations with Missing Addends

Complete the following equation:

$1000+\Box=1100$

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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:

$1000+\Box=1100$

Step-by-step solution

To solve the equation $1000 + \Box = 1100$ , we need to determine the value of $\Box$ that makes the equation true.

Step 1: Recognize that the equation has the format $a + b = c$ .
Step 2: Identify the known values:
- $a = 1000$
- $c = 1100$
Step 3: Rearrange the equation to solve for the missing number $\Box$ :
$\Box = c - a = 1100 - 1000$
Step 4: Perform the calculation:
$1100 - 1000 = 100$

Therefore, the missing number $\Box$ is $100$ .

Selecting from the given choices:

Choice 1: $1$ - Incorrect.
Choice 2: $10$ - Incorrect.
Choice 3: $100$ - Correct.
Choice 4: $1000$ - Incorrect.

Thus, the correct choice is Choice 3: $100$ .

Final Answer

$100$

Key Points to Remember

Essential concepts to master this topic

Equation Structure: In a + b = c, isolate the unknown by subtracting
Technique: Rearrange to $\Box = 1100 - 1000 = 100$
Check: Substitute back: $1000 + 100 = 1100$ ✓

Common Mistakes

Avoid these frequent errors

Adding instead of subtracting to isolate the unknown
Don't add 1000 + 1100 = 2100! This gives a completely wrong answer because you're combining known values instead of finding the difference. Always subtract the known addend from the sum to find the missing addend.

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 1000 from 1100 instead of adding them?

Because we need to isolate the unknown! Think of it like this: if 1000 + something = 1100, then that 'something' must be the difference between 1100 and 1000.

How can I check if 100 is really the right answer?

Simple! Just substitute 100 back into the original equation: $1000 + 100 = 1100$ . Since both sides equal 1100, your answer is correct!

What if the missing number was in a different position?

The method stays the same! Whether it's $\Box + 1000 = 1100$ or $1000 + \Box = 1100$ , you still subtract the known addend from the sum to find the missing one.

Is there a pattern with numbers ending in zeros?

Yes! When working with round numbers like 1000 and 1100, focus on the hundreds place. The difference is 1100 - 1000 = 100, which makes sense because 11 - 10 = 1 hundred.

What if I picked 1000 as my answer by mistake?

Let's check: $1000 + 1000 = 2000$ , not 1100! Always verify your choice by substituting it back into the original equation.

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