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Probability problems

I need help solving probability problems, especially with the question below.

The life expectancy of a laptop is normally distributed with a mean of 48 months and a standard deviation of 6 months.

What is the probability that a randomly selected laptop will be in working condition after 5 years?

What percentage of laptops will last less than 48 months?

If the manufacturer guarantees the laptops for 3 years and will replace if malfunction, what percentage of laptops will need to be replaced?

95% of the laptops will have a life expectancy of at least how many months?

Solution Summary

This solution gives the step by step method for computing probabilities based on Z score.