Solve the Equation: Finding the Triangle's Value in 30 + △ = 38

Basic Equations with Unknown Variables

Determine the numerical value of the triangle:

30+=38 30+{\triangle}=38

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Determine the numerical value of the triangle:

30+=38 30+{\triangle}=38

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the known numbers in the equation.
  • Step 2: Rearrange the equation to solve for the unknown value.
  • Step 3: Calculate using basic subtraction.

Now, let's work through each step:
Step 1: The known numbers in the equation are 3030 and 3838. We need to find \triangle in 30+=3830 + \triangle = 38.
Step 2: Rearrange the equation to isolate \triangle: =3830 \triangle = 38 - 30 .
Step 3: Calculate the difference: =8 \triangle = 8 .

Therefore, the value of the triangle is 8 8 .

3

Final Answer

8 8

Key Points to Remember

Essential concepts to master this topic
  • Isolation: Move all known numbers to one side of the equation
  • Technique: Subtract 30 from both sides: 38 - 30 = 8
  • Check: Substitute back into original equation: 30 + 8 = 38 ✓

Common Mistakes

Avoid these frequent errors
  • Adding instead of subtracting to isolate the variable
    Don't add 30 to both sides when solving 30 + △ = 38, getting △ = 68! This makes the equation unbalanced because you're not undoing the addition. Always use the opposite operation - subtract 30 from both sides to isolate △.

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 I subtract 30 instead of adding it?

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To isolate the triangle, you need to undo what's being done to it. Since 30 is being added to the triangle, you subtract 30 from both sides to cancel it out.

What does the triangle symbol represent?

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The triangle \triangle is just a placeholder for an unknown number - like using x or y. It could be any shape or letter, but it represents the same thing: a mystery value to solve for.

How do I know which operation to use?

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Look at what operation is connecting the unknown to the known number. If it's addition (+), use subtraction (-). If it's subtraction (-), use addition (+).

Can I check my answer a different way?

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Yes! You can also think: "What number plus 30 equals 38?" Count up from 30 to 38, and you'll get 8. This confirms your algebraic solution.

What if I get a negative answer?

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Negative answers are perfectly valid! For example, if the equation was 50+=45 50 + \triangle = 45 , then =5 \triangle = -5 . Always check by substituting back.

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