# (i) 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?

(ii) Suppose the bulb drawn in (i) 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:**

Total number of bulbs = 20

Number of defective pieces = 4

(i) Probability that the bulb is defective = Number of possible outcomes/Number of favourable outcomes

= 4/20 = 1/5

(ii) Suppose the bulb drawn in (i) is not defective and is not replaced.

Remaining number of bulbs = 20 - 1 = 19

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

The probability that this bulb is not defective = Number of possible outcomes/Total number of favourable outcomes

= 15/19

Check out more in terms of probability.

**Video Solution:**

## (i) 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? (ii) Suppose the bulb drawn in (i) 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 ?

### NCERT Solutions for Class 10 Maths Chapter 15 Exercise 15.1 Question 17 - Chapter 15 Exercise 15.1 Question 17:

**Summary:**

(i) A lot of 20 bulbs contain 4 defective ones. One bulb is drawn at random from the lot. The probability that this bulb is defective is 1/5, and (ii) Suppose the bulb drawn in (i) is not defective and is not replaced and a bulb is picked randomly then the probability that this bulb is not defective is 15/19.