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Stats-crv-exponential distribution

  1. Feb 10, 2013 #1
    1. The problem statement, all variables and given/known data

    The time to failure for a certain light bulb in constant failure rate mode has a mean time to failure of 5000 hours.

    What is the probability that a randomly chosen light bulb is still burning after 10,000 hours? Give answer to 4 decimals.

    If 5 light bulbs are installed in different street lamps along Main Street, what is the probability that at least 1 will be working after 10,000 hours? Give answer to 4 decimals.
    Response:

    3. The attempt at a solution
    I believe the first part would simply be e-(1/5000*10000)=.1353

    The second part I am at a loss on how to solve it.
     
  2. jcsd
  3. Feb 10, 2013 #2

    haruspex

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    Can you construct the logical inverse of 'at least one still working'?
     
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