In the Simple Units environment, any verifications of valid dimensions ignore so-called Unit annotations.

In the Simple Units environment, the max and min procedures override the top-level max and min procedures.  If any of the arguments have units associated with them, all units are converted to the units of the first argument, and then the global procedure of the same name is called on the unitless arguments.

Every command in the Simple Units environment that needs to determine whether an expression is valid or not, does so using the Units:-TestDimensions command.

To enter a unit in 2-D Math input, select the unit from the appropriate Units palette. If the unit you want is not there, select $\mathrm{unit}$ and then enter the unit.

When you edit a unit, double brackets appear around it.

$\mathrm{with}\left(\mathrm{Units}\left[\mathrm{Simple}\right]\right)\:$

$\min \left(\frac{3}{2}\mathrm{Unit}\left('m'\right)\,1.49\mathrm{Unit}\left('\mathrm{ft}'\right)\right)$

$1.49⟦\mathrm{ft}⟧$

$\mathrm{dis}≔\max \left(x\mathrm{Unit}\left('\mathrm{furlong}'\right)\,\frac{3}{2}\mathrm{Unit}\left('\mathrm{ft}'\right)\,120\mathrm{Unit}\left('\mathrm{cm}'\right)\,17\mathrm{Unit}\left('\mathrm{inches}'\right)\right)$

$\mathrm{dis}≔\max \left(\frac{6}{5}\,\frac{25146x}{125}\right)⟦m⟧$

$x≔3$

$x≔3$

$\mathrm{dis}$

$\frac{75438}{125}⟦m⟧$