Only the SI units and those units recognized for use with SI are used to express quantities. Equivalent values in other units, given in parentheses following the SI units are allowed only when necessary for the reader.
Symbols are unaltered when expressing plural quantities.
The length of the bar is 75 cm. The bar is 75 cm long. Incorrect The bar is 75 cm. A slash, if used, must not appear more than once in the same expression unless parentheses are used, to avoid ambiguities. Variables and quantity symbols are in italics.