MATLAB: How to simplify unit fractions

MATLABsymbolicSymbolic Math Toolbox

u1 = symunit;
u2 = symunit;
x=2*u1.meter;
y=5*u2.millimeter;
frac=x/y
double(frac)
Results in 
frac = 
(2/5)*([m]/[mm])
Error using symengine
Unable to convert expression into double array.
Error in sym/double (line 700)
        Xstr = mupadmex('symobj::double', S.s, 0);
But should result in 
frac = 
400

Best Answer

 simplify(frac)
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