Three numbers are chosen from `1` to `20`. Find the probability that they are consecutive.

Explanation

Let, `E=` Total number of favorable cases


`n(E)=18`


`S=` Total number of cases


`n(E)=20_(C_3)`


`n(E)=(20 times 19 times 18)/(3 times 2 times 1)`


`n(E)=1140`


`therefore` Required probability `= (18)/(1140)=(3)/(190)`


`(Answer)`