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Question
Cards numbered 1 to 30 are put in a bag. A card is drawn at random from the bag. Find the probability that the number on the drawn card is not divisible by 3,
Solution
Total number of outcomes = 30.
Let E1 be the event of getting a number not divisible by 3.
Out of these numbers, numbers divisible by 3 are 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30.
Number of favourable outcomes = 30 − 10 = 20
∴ P(getting a number not divisible by 3) = P(E1) = `("Number of outcomes favourable to" E_1)/"Number of all possible outcomes"`
`= 20/30 = 2/3`
Thus, the probability that the number on the card is not divisible by 3 is `2/3`.
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