# Multiplication With Signed Numbers

Learn how to perform multiplication with two's complement numbers.

## We'll cover the following

## Multiplication technique

To multiply two’s complement numbers we employ the same technique we used in the lesson Multiplication in Binary, with some minor changes.

Before carrying out the multiplication, we *sign-extend* the number to twice as many bits. This simply means that we add $n$ copies of the sign bit to the left of the number, where $n$ is the number of bits in the original number. For example:

$10001000$ would be sign-extended to $1111111110001000$.

After this, we carry out the multiplication as before. We take the $n$ **least-significant bits** of the product as our final answer.

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