Solve the Equation: Finding the Missing Number in ?-0=27

Q: Why doesn't subtracting zero change the number?

The identity property of subtraction states that any number minus zero equals itself. Think of it like taking away nothing - you still have the same amount! So $ 5 - 0 = 5 $, $ 100 - 0 = 100 $, and $ 27 - 0 = 27 $.

Q: Is this different from adding zero?

Both addition and subtraction with zero are identity properties! Adding zero: $ x + 0 = x $. Subtracting zero: $ x - 0 = x $. Both leave the original number unchanged.

Q: How do I check if 27 is correct?

Substitute 27 back into the original equation: $ 27 - 0 = ? $. Since $ 27 - 0 = 27 $ and we needed the result to be 27, our answer is correct!

Q: Are there other numbers that work?

No, only 27 works! In the equation $ ? - 0 = 27 $, the unknown value must equal exactly 27. Try any other number like 26 or 28, and you won't get 27 as the result.

Identity Property with Zero Subtraction

$?-0=27$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:04 Let's find the mystery number.

00:08 Remember, taking zero away from a number leaves it the same.

00:16 And that's how we solve the problem.

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$?-0=27$

Step-by-step solution

To solve this problem, let's apply the identity property of subtraction:

We are given the equation $x - 0 = 27$ .
According to the identity property of subtraction, subtracting zero from any number does not change its value. Hence, $x - 0 = x$ .

Therefore, the equation simplifies to $x = 27$ .

The solution to the problem is $x = 27$ , confirming that substitution gives the desired outcome.

Final Answer

Key Points to Remember

Essential concepts to master this topic

Identity Property: Subtracting zero from any number leaves it unchanged
Technique: Simplify $x - 0 = 27$ becomes $x = 27$
Check: Substitute back: $27 - 0 = 27$ ✓

Common Mistakes

Avoid these frequent errors

Adding zero instead of recognizing the identity property
Don't think ? + 0 = 27 so ? = 27 - 0 = 27! This adds an unnecessary step and can create confusion. Always recognize that subtracting zero doesn't change the number, so ? - 0 = 27 means ? = 27 directly.

Practice Quiz

Test your knowledge with interactive questions

$1\times1000=$

FAQ

Everything you need to know about this question

Why doesn't subtracting zero change the number?

The identity property of subtraction states that any number minus zero equals itself. Think of it like taking away nothing - you still have the same amount! So $5 - 0 = 5$ , $100 - 0 = 100$ , and $27 - 0 = 27$ .

Is this different from adding zero?

Both addition and subtraction with zero are identity properties! Adding zero: $x + 0 = x$ . Subtracting zero: $x - 0 = x$ . Both leave the original number unchanged.

What if the equation was ? + 0 = 27 instead?

The answer would still be 27! Whether you add zero or subtract zero, the result is the same because of the identity properties. $x + 0 = 27$ and $x - 0 = 27$ both give $x = 27$ .

How do I check if 27 is correct?

Substitute 27 back into the original equation: $27 - 0 = ?$ . Since $27 - 0 = 27$ and we needed the result to be 27, our answer is correct!

Are there other numbers that work?

No, only 27 works! In the equation $? - 0 = 27$ , the unknown value must equal exactly 27. Try any other number like 26 or 28, and you won't get 27 as the result.

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