Solve the Addition Expression: Finding the Sum of 19 + 30

Equivalent Expressions with Number Substitution

Which expression is equivalent to the given equation?

19+30= 19+30=

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Step-by-step written solution

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1

Understand the problem

Which expression is equivalent to the given equation?

19+30= 19+30=

2

Step-by-step solution

To solve this problem, we need to find which expression is equivalent to the equation 19+30 19+30 .

Let's first compute the sum:

  • Calculate 19+30 19 + 30 .
    This gives us 49 49 .

Next, let's look at the given answer choices and determine which expression results in 49 49 :

Choice 1: (20+301)(20+30-1)

  • Calculate 20+30=50 20 + 30 = 50 .
  • Subtract 1 1 from 50 50 : So, 501=49 50 - 1 = 49 .
  • The expression 20+301 20+30-1 results in 49 49 .

Therefore, the equivalent expression to 19+30 19+30 is 20+301 20+30-1 .

3

Final Answer

20+301 20+30-1

Key Points to Remember

Essential concepts to master this topic
  • Rule: Equivalent expressions must have the same numerical value
  • Technique: Replace 19 with 20-1: 19+30=(201)+30 19+30 = (20-1)+30
  • Check: Calculate both expressions: 19+30=49 19+30=49 and 20+301=49 20+30-1=49

Common Mistakes

Avoid these frequent errors
  • Adding or subtracting wrong amounts when substituting
    Don't change 19 to 20+1 = getting 51 instead of 49! This happens when you add instead of subtract to compensate. Always remember: if you increase one number, you must subtract that same amount elsewhere.

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 would I want to change 19 to something else?

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Changing numbers can make mental math easier! For example, 20+30 is simpler to calculate than 19+30, so we substitute and adjust.

How do I know what to add or subtract when substituting?

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If you increase a number, you must subtract the same amount somewhere else. If 19 becomes 20 (+1), you must subtract 1 to keep the expression equal.

Can I change both numbers in the expression?

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Yes! But be careful to balance your changes. If you change 19 to 20 (+1) and 30 to 29 (-1), the total stays the same.

What if I get a different answer than 49?

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Double-check your substitution! Make sure you're adding and subtracting the right amounts. The original 19+30=49 19+30=49 , so your equivalent expression must also equal 49.

Are there other ways to write equivalent expressions?

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Absolutely! You could write 18+31 18+31 , 10+39 10+39 , or many others. As long as they equal 49, they're equivalent!

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