Expand 3,508.
Incorrect answer: 3,000 + 50 + 8
An omitted term in expanded form can still require a zero digit in standard form. Writing 2,000 + 6 as 26 loses the thousands place.
Dropping a zero from a number
A missing expanded-form term can still need a zero in the written number. Check the place-value columns.
The correction
3,000 + 500 + 8
The tens place contributes zero.
- Make a place-value chart for thousands, hundreds, tens, and ones.
- Write each nonzero place as a value in expanded form.
- Read the number in words and convert it back to digits to check.
Try the reasoning in another example
Write three thousand fifty-two in standard form.
- Three thousand gives 3 in the thousands place; fifty-two gives 5 tens and 2 ones.
- There are no hundreds, so put 0 in that place.
Answer: 3,052
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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