Expand 526.
Incorrect answer: 5 + 2 + 6
Expanded form is not a list of digits: 352 is 300 + 50 + 2, not 3 + 5 + 2. Include a zero in standard form when a place is empty.
Writing digits instead of expanded values
Expanded form shows the value contributed by each place. Empty places still need zeros in standard form.
The correction
500 + 20 + 6
Each digit is multiplied by its place value.
- Read each digit with its place, not just its face value.
- Write the value of the hundreds, tens, and ones.
- Add the parts; a zero-value term may be included or omitted.
Try the reasoning in another example
Expand 407.
- There are four hundreds, zero tens, and seven ones.
- The tens term contributes nothing.
Answer: 400 + 7
Explain why each step preserves the quantity or relationship. If you can compute the answer but cannot explain the step, revisit the model before adding more questions.
The short check below reuses the first example as a retrieval question and adds a second question. It checks this method; it does not establish a grade level.
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