If 3 dice are rolled then the probability of getting different numbers or sum 16 is

Sum=16

$\left(556\right)\to \frac{3!}{2!}=3$

$\left(664\right)\to \frac{3!}{2!}=3$

$different\to \mathrm{6.5.4}$

$P\left(E\right)=\frac{\mathrm{6.5.4}+6}{6\times 6\times 6}$

             $=\frac{7}{12}$