A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box..
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.
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Answer:
Total numbers of discs = 50
(i) Total numbers of favourable events = 81
Probability that it bears a two-digit number = 81/90 = 9/10
(ii) Perfect square numbers = 1, 4, 9, 16, 25, 36, 49, 64 and 81
Favourable numbers of events = 9
Probability of getting a perfect square number = 9/90 = 1/10
(iii) Numbers which are divisible by 5 = 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85 and 90
Favourable numbers of events = 18
Probability of getting a number divisible by 5 = 18/90 = 1/5
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