### A good answer might be:

>       1
>     0001 0000     1610
>     1001 1000    -2410
>     ---------    ----
>     1010 1000    -4010 (wrong!)

# Patterns that Add Up to Zero

The "binary addition algorithm" does NOT work with sign-magnitude. There are algorithms that do work with sign-magnitude, and some early computers were built to use them. (And other computers were built using other not-ready-for-prime-time algorithms). It took several years of experience for computer science to decide that a better way had to be found.

There is a better way. Recall a question and its answer from several pages ago:

>       11111 111
>        0000 0001  =   110
>        1111 1111  =   ?
>        ---------      -----
>        0000 0000  =   010

### QUESTION 14:

A number added to one results in a zero. What could that number be?