Correctly write a 0 in the quotient whenever a divisor does not fit into a bring-down amount at all.
Sometimes the divisor simply does not fit into a digit at all. That place in the quotient still gets a written 0, and then you bring down the next digit and keep going exactly as before.
Skipping that zero instead of writing it shifts every digit after it into the wrong place value, which changes the size of the whole answer.
Mastery looks like: They correctly write a 0 in the quotient whenever a divisor does not fit into a bring-down amount, keeping every place value correct.
Common stumbles: Leaving out the zero and shifting later digits into the wrong place; forgetting to bring down the next digit after writing a zero.
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