10) 724x999=724x(1000-1)=
=724x1000-724x1=
724000-724=
=723 270
380x999=380x(1 000-1)=
=380x1000-380x1=
=380 000=380=
=379 620
405x999=405x(1000-1)=
=405x1000-405x1=
=405 000-405=
=404 595
b) 657x999=657x(1000-1)=
=656x1000-657x1=
=657 000-657=
=656 343
813x999=813x(1000-1)=
=813x1000=813x1=
=813 000-813=
=812 187
678x999=678x(1000-1)
=678x1000-678x1=
=678 000-678=
=677 322
