Multiplication of multi-digit whole numbers is understood as combining place-value-scaled partial products: each digit of one factor multiplies the other factor, and its place determines the corresponding shift in the written product. The standard algorithm records these products compactly, uses regrouping when products exceed nine, and combines them accurately; estimation and place-value reasoning help detect misplaced digits or omitted regrouping. This treatment excludes decimal, fraction, and algebraic extensions.
Each digit in one factor creates a partial product. Its place value tells you where that product belongs. Start with the ones digit, then move left.
Example:
First, multiply by the ones digit, :
So,
Next, multiply by the tens digit, . Since represents , the answer belongs one place to the left:
This gives , shifted one place left, or .
Write and add the partial products:
Therefore,
Check your answer with an estimate:
Since is close to , the answer is reasonable.
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