A city installs 2000 electric lamps for street lighting. These lamps have a mean burning life of 1000 hours with a standard deviation of 200 hours. Assume that the burning life is approximately normally distributed. a.) What is the probability that a lamp will not fail in the first 700 burning hours? b.) How many lamps are expected to fail between 800 and 1200 burning hours? c.) After how many burning hours would we expect approximately 10% of the lamps to be left?

A city installs 2000 electric lamps for street lighting. These lamps have a mean burning life of 1000 hours with a standard deviation of 200 hours. Assume that the burning life is approximately normally distributed. a.) What is the probability that a lamp will not fail in the first 700 burning hours? b.) How many lamps are expected to fail between 800 and 1200 burning hours? c.) After how many burning hours would we expect approximately 10% of the lamps to be left?

College Algebra

10th Edition

ISBN:9781337282291

Author:Ron Larson

Publisher:Ron Larson

Chapter8: Sequences, Series,and Probability

Section8.7: Probability

Problem 11ECP: A manufacturer has determined that a machine averages one faulty unit for every 500 it produces....

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