we multiply the digits different from 0
[tex]1\times9=9[/tex]and now add the total of zeros=9
[tex]9.000.000.000[/tex]a diferent exercise
[tex]200\times320[/tex]
you multiply 2x32 and add 3 zeros
the solution is
[tex]2\times32=64[/tex]with the zeros
[tex]64000[/tex]