Multiplying a whole number from 100–999 by one from 10–99 involves decomposing the factors by place value and combining partial products through the distributive property, with regrouping when needed. Area models, equations, and the standard algorithm show why the tens partial product is shifted one place and support estimation to check reasonableness; this scope excludes decimal factors, larger or more general multidigit cases, and symbolic extensions.
To multiply a 3-digit number by a 2-digit number, break the 2-digit number into tens and ones. Then multiply the 3-digit number by each part and add the partial products.
Example: Find .
The number has tens and ones:
So,
Multiply by the ones:
Multiply by the tens:
The zero appears because is tens, not ones.
Therefore,
Using the standard algorithm, the work looks like this:
The second row is shifted one place to the left because it represents tens.
You can estimate to check your answer:
Since is reasonably close to , the answer makes sense.
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