A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears (i) a two-digit number (ii) a perfect square number (iii) a number divisible by 5

i) Number of 2-digit numbers from 1 to 90 = 81.
P(2-digit number) = 81/90 = 9/10
ii) Number of perfect squares between 1 and 90 = (1, 4, 9, 16, 25, 36, 49, 64, 81) = 9
P(Perfect square) = 9/90 = 1/10
iii) Multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90
Number of multiples of 5 = 18
P(Multiples of 5) = 18/90 = 1/5