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10% of the bulbs produced in a factory are of red colour and 2% are red and defective. If one bulb is picked up at random, determine the probability of its being defective if it is red.

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Question

10% of the bulbs produced in a factory are of red colour and 2% are red and defective. If one bulb is picked up at random, determine the probability of its being defective if it is red.

Sum
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Solution

Let A and B be the events that the bulb is red and defective, respectively

P(A) = `10/100 = 1/10`.

P(A ∩ B) = `2/100 = 1/50`

P(B|A) = `("P"("A" ∩ "B"))/("P"("A"))`

= `1/50 xx 10/1`

= `1/5`

Thus the probability of the picked up bulb of its being defective, if it is red, is `1/5`.

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Chapter 13: Probability - Solved Examples [Page 262]

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NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 13 Probability
Solved Examples | Q 3 | Page 262

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