NCERT Mathematics Class 9 Exemplar Ch 14 Statistics and Probability Part 12

Get unlimited access to the best preparation resource for CBSE/Class-6 Social-Sciences: fully solved questions with step-by-step explanation- practice your way to success.

Q.18. Bulbs are packed in cartons each containing 40 bulbs. Seven hundred cartons were examined for defective bulbs and the results are given in the following table:

Bulbs are packed in cartons each containing 40 bulbs

Number of defective bulbs

0

1

2

3

4

5

6

more than 6

Frequency

400

180

48

41

18

8

3

2

One carton was selected at random. What is the probability that it has?

(i) No defective bulb?

(ii) Defective bulbs from 2 to 6?

(iii) Defective bulbs less than 4?

Answer: (i) (ii) (iii)

Q.19. Over the past 200 working days, the number of defective parts produced by a machine is given in the following table:

Over the past 200 working days, the number of defective parts produced by a machine

Number of defective parts

0

1

2

3

4

5

6

7

8

9

10

11

12

13

Days

50

32

22

18

12

12

10

10

10

8

6

6

2

2

Determine the probability that tomorrow’s output will have

(i) No defective part

(ii) At least one defective part

(iii) Not more than 5 defective parts

(iv) More than 13 defective parts

Answer: (i) (ii) (iii) (iv)

Q.20. A recent survey found that the ages of workers in a factory is distributed as follows:

A recent survey found that the ages of workers in a factory is distributed

Age (in years)

20 - 29

30 - 39

40 - 49

50 - 59

60 and above

Number of workers

38

27

86

46

3

If a person is selected at random, find the probability that the person is:

(i) 40 years or more

(ii) Under 40 years

Answer: (i) (ii) (iii) (iv)