Solve the Addition Equation: Finding the Missing Number in □ + 30 = 42

Symbol Substitution with Basic Addition

If:

=12 \colorbox{yellow}\\=12

Solve the following addition problem:

+30= \colorbox{yellow}\\+30=

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

If:

=12 \colorbox{yellow}\\=12

Solve the following addition problem:

+30= \colorbox{yellow}\\+30=

2

Step-by-step solution

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

  • Step 1: Recognize that the yellow shape represents the number 12.
  • Step 2: Replace the shape in the equation with its numeric value.
  • Step 3: Perform the addition.

Now, let's work through these steps:
Step 1: The problem states that the yellow shape is equivalent to 12 12 .
Step 2: We replace the yellow shape with 12 12 in the addition equation.
Step 3: Solve the equation 12+30=42 12 + 30 = 42 . This addition gives us the solution.

Therefore, the solution to the problem is 42 42 .

3

Final Answer

42 42

Key Points to Remember

Essential concepts to master this topic
  • Symbol Rule: Replace the given symbol with its numeric value
  • Technique: Substitute 12 for yellow shape: 12 + 30 = 42
  • Check: Verify the symbol equals 12, then confirm 12 + 30 = 42 ✓

Common Mistakes

Avoid these frequent errors
  • Ignoring the symbol's given value
    Don't treat the yellow shape as an unknown variable to solve for = confusion about what to find! The problem already tells you the shape equals 12. Always use the given symbol value and perform the indicated operation.

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 is the yellow shape given a value at the beginning?

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The problem is testing your ability to substitute known values into expressions. It's like a code where the yellow shape represents the number 12.

Is this the same as solving for an unknown?

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No! This is substitution, not solving. The symbol already has a known value (12), so you just replace it and calculate.

What if I forget what the symbol represents?

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Always look back at the given information at the start of the problem. Write down what each symbol equals before you begin calculating.

How do I avoid making calculation errors?

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After substituting, double-check your arithmetic: 12+30 12 + 30 . Count up from 12 by tens: 12, 22, 32, 42. Or use 10+30=40 10 + 30 = 40 , then add the remaining 2.

Can symbols represent different numbers in other problems?

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Yes! Each problem defines what its symbols mean. Always read the given information carefully - the same shape might equal different numbers in different problems.

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