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

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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
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
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
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)

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