if the side oof a square is a units then the length of its diagonal is d=asqrt(2)
in our case we have a=10sqrt(6) so the diagonal will be 10sqrt(6)sqrt(2) =====>> 10sqrt(12)
or 10sqrt(3*4) ===>>> 10*2sqrt(3) ====>>> 20sqrt(3) and since sqrt(3)=1.732 approx.
the diagonal will be 20*1,732 = 34.64 units approx