Although vanilla CSS now also offers this feature in the form of calc(), the Sass alternative is quicker to write, has the modulo % operation, and can be applied to a wider range of data-types (e.g. colors and strings). 

$width: 800px;

.container { 
  width: $width;

.column-half {
  width: $width / 2;

.column-fifth {
  width: $width / 5;
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