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Question
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 a number divisible by 5.
Solution
Total number of discs = 90
Numbers that are between 1 and 90 and divisible by 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, and 90.
Therefore, total numbers divisible by 5 = 18
Numbers of favourable outcomes = 18
Probability of getting a number divisible by 5 = `"Number of favourable outcomes"/"Total number of possible outcomes" = 18/90 = 1/5`
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