NCERT Mathematics Class 9 Exemplar Ch 14 Statistics and Probability Part 12 (For CBSE, ICSE, IAS, NET, NRA 2022)
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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:
| 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:
| 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:
| 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)