# 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? - Mathematics

Sum

1) 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?

2) Suppose the bulb drawn in (1) is not defective and is not replaced. Now one bulb is drawn at random from the rest. What is the probability that this bulb is not defective?

#### Solution

(1) Total number of bulbs = 20

Total number of defective bulbs = 4

P (getting a defective bulb) = 4/20 = 1/5

(2) Remaining total number of bulbs = 19

Remaining total number of non-defective bulbs = 16 − 1 = 15

P (getting a not defective bulb) = 15/19

Concept: Probability - A Theoretical Approach
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Chapter 16: Probability - Exercise 16.1 [Page 25]

#### APPEARS IN

RD Sharma Class 10 Maths
Chapter 16 Probability
Exercise 16.1 | Q 57 | Page 25
NCERT Class 10 Maths
Chapter 15 Probability
Exercise 15.1 | Q 17 | Page 309

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