Question

A box contains 20 discs which are numbered from 1 to 20. If one disc is drawn at random from the box, then find the probability that the number the drawn disc is a 2-digit number.

Answer 1

S = {1, 2, 3, 4, 5, ... 20}

∴ n(S) = 20

2 digit number {10, 11, 12, ... 20}

∴ n(E) = 11

Required probability = `(n(E))/(n(S)) = 11/20`