A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and
distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of
77) At least 500 hours

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  1. A normal distribution is symmetrical about the mean, which means that 50% of the cases are above the mean, and 50%, below.

    So how many % of the lightbulbs will last at least 500 hours?

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