Simple columns in Sass

sass-simple-columns.scss

@mixin set-columns($numCols, $margin:0, $padding-sides:0) {
  $afterPadding: 100% - (($numCols - 1) * $margin);

  float: left;
  width: $afterPadding/$numCols;
  margin-right: $margin;
  padding-left: $padding-sides/2;
  padding-right: $padding-sides/2;

  &:nth-of-type(#{$numCols}n + #{$numCols}) {
    margin-right: 0;
  }
  &:nth-of-type(#{$numCols}n - #{($numCols * 2) - 1}) {
    clear: both;
  }
}