Solve for Triangle: Finding the Missing Value in 33 + △ = 40

Basic Algebraic Equations with Symbol Substitution

Determine the numerical value of the triangle:

33+=40 33+\triangle=40

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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:

33+=40 33+\triangle=40

2

Step-by-step solution

To solve the equation 33+=40 33 + \triangle = 40 , we will follow these steps:

  • Step 1: Write down the equation: 33+=40 33 + \triangle = 40 .
  • Step 2: Subtract 33 from both sides to isolate \triangle :
  • =4033 \triangle = 40 - 33 .
  • Step 3: Perform the subtraction: 4033=7 40 - 33 = 7 .

Therefore, the numerical value of the triangle \triangle is 7 7 .

Accordingly, the correct answer choice is 7 7 , which matches choice 4.

3

Final Answer

7 7

Key Points to Remember

Essential concepts to master this topic
  • Isolation Rule: Move numbers to opposite side using inverse operations
  • Technique: Subtract 33 from both sides: 4033=7 40 - 33 = 7
  • Check: Substitute back into original equation: 33+7=40 33 + 7 = 40

Common Mistakes

Avoid these frequent errors
  • Adding instead of subtracting to isolate the variable
    Don't add 33 to both sides when trying to isolate △ = 73! This moves numbers in the wrong direction and increases the equation instead of isolating the unknown. Always use the opposite operation to move numbers across the equals sign.

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 33 instead of adding it?

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Since 33 is being added to the triangle, you need to do the opposite operation (subtraction) to cancel it out. Think of it as undoing what's already there!

What does the triangle symbol represent?

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The triangle \triangle is just a placeholder for an unknown number, like using 'x' in algebra. It represents the missing value we need to find.

Can I solve this by counting up from 33?

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Yes! You can count: 33 + ? = 40. Count up from 33 to 40: 34, 35, 36, 37, 38, 39, 40. That's 7 steps, so △ = 7.

How do I check if 7 is correct?

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Replace the triangle with 7 in the original equation: 33+7=40 33 + 7 = 40 . Since 40 = 40 is true, your answer is correct!

What if I get a different answer choice?

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Double-check your arithmetic! The most common error is using the wrong operation. Remember: to isolate △, you must subtract 33 from both sides.

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