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Question
80 bulbs are selected at random from a lot and their life time (in hrs) is recorded in the form of a frequency table given below :
| Life time (in hours) | 300 | 500 | 700 | 900 | 1100 |
| Frequency | 10 | 12 | 23 | 25 | 10 |
The probability that bulbs selected randomly from the lot has life less than 900 hours is:
Options
`11/40`
`5/16`
`7/16`
`9/16`
Solution
`bb(9/16)`
Explanation:
Total number of bulbs in a lot, n(S) = 80
Number of bulbs whose life time is less than 900 h, n(E) = 10 + 12 + 23 = 45
Probability that bulbs has life time less than 900 h = `(n(E))/(n(S)) = 45/80 = 9/16`
Hence, the probability that bulb has life time less than 900 is `9/16`.
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