SOLUTION: 1000 light bulbs with a main life of 120 days are installed.
a) How many bulbs will expire in less than 90 days?
Sketch the graph
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-> SOLUTION: 1000 light bulbs with a main life of 120 days are installed.
a) How many bulbs will expire in less than 90 days?
Sketch the graph
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Question 1121250: 1000 light bulbs with a main life of 120 days are installed.
a) How many bulbs will expire in less than 90 days?
Sketch the graph Answer by ikleyn(52781) (Show Source):
You can put this solution on YOUR website! .
1000 light bulbs with a mean life of 120 days are installed.
a) How many bulbs will expire in less than 90 days?
Sketch the graph
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First of all, pay attention on how I edited your post.
From the first glance, it is clear that the given info/input is NOT SUFFICIENT to solve the problem - appropriate
auxiliary assumptions should be made.
Moreover, making appropriate and likelihood assumptions is the PART of the solution.
I will assume that this part of the condition "mean life of 120 days" can be interpreted as "all 1000 light bulbs will expire in 240 days".
It is first assumption. The second assumption is that the life time is distributed uniformly during this period of 240 days.
Notice that the second assumption is consistent with the first one (!)
If so, then the proportion works
= ,
which gives x = = 375.
Answer. Under the proposed / accepted assumptions, 375 light bulbs will expire in 90 days.
