An example:

evalf(frac(10^2*exp(1)));

0.8281828

Two digits lost.

And here is even worse:

evalf(frac(10^9*exp(1)));

0.

Correct unswer:

evalf[20](frac(10^9*exp(1)));

0.4590452354

The correct answer

The following simple procedure: 
SubsColumn: = proc (A, V, k) 
local B, m; 
with (LinearAlgebra); 
m: = ColumnDimension (A); 
B: = <A[..,1..m]|V>; 
B: = ColumnOperation (B, [k, m +1]); 
B: = DeleteColumn (B, m +1); 
B; 
end proc; 

solve the problem of...