To multiply two numbers using partial products, you have to:
Compute one-by-one the partial products. In our case, these are:
20 × 10 = 200;
20 × 2 = 40;
8 × 10 = 80; and
8 × 2 = 16.
Add all the partial products together:
200 + 40 + 80 + 16 = 336,
which is the final answer to 28 × 12.
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