From first 20 natural numbers if two numbers are selected at random then the probability of selecting them which are not consecutive is

From first 20 natural numbers  two numbers are selected at random

$n\left(S\right)={ }^{20}{C}_2=190$

E= Event of selecting them which are not consecutive 

$\overline{\mathrm{E}}$= Event of selecting them which are  consecutive 

$\overline{E}=\left\{\left(1,2\right),\left(2,3\right),.....\left(19,20\right)\right\}$

$n\left(\overline{E}\right)=19$

$P\left(E\right)=1-P\overline{\left(E\right)}=1-\frac{19}{190}=1-\frac{1}{10}=\frac{9}{10}$