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.

Explanation

The total numbers of discs `= 50`

P(E) = (Number of favourable outcomes/ Total number of outcomes)


(i) Total number of discs having two digit numbers` = 81`

(Since `1` to `9` are single digit numbers and so, total `2` digit numbers are `90-9 = 81`)
P (bearing a two-digit number) `= 81/90 = 9/10 = 0.9`

(ii) Total number of perfect square numbers` = 9 (1, 4, 9, 16, 25, 36, 49, 64 and 81)`


P (getting a perfect square number)` = 9/90 = 1/10 = 0dot1`

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