9.1.2 Computing with units
Xcas performs usual arithmetic operations (+, , *, /, ^
) on
unit objects. Different units may be used, but they must be
compatible for + and . The result is an unit object

for the
multiplication and the division of two unit objects
_u1 and _u2 the unit of the result is written
_(u1*u2) or _(u1/u2).
 for an addition or a subtraction of compatible unit objects,
the result is expressed with the same unit as the first term of the operation.
Input :
1_m+100_cm
Output :
2_m
Input :
100_cm+1_m
Output :
200_cm
Input :
1_m*100_cm
Output :
1_m^
2