A lot of 20 bulbs contain 4 defective ones. One bulb is drawn at random from the lot. What is the probability that this bulb is defective?

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15

35

45

13

answer is A.

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Detailed Solution

Given that there are 20 bulbs out of which 4 are defective.
The Probability of occurrence of an event E is

P (E) = n (E) n (S)

.
According to the question,
Total bulbs

= n S = 20

.
Defective bulbs

= n E = 4

.
P (Defective bulb)

= P (E)

P (E) = n (E) n (S) = 420 = 15

.
Hence, the probability of a defective bulb is

15

.
Therefore, option 1 is correct.

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