percentage with standard deviation

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• February 19th 2011, 02:59 PM
systusem
percentage with standard deviation
The question is:
...
Many snails have a one-mile race, and the time it takes for them to finish is approximately normally distributed with mean 50 hours and standard deviation 6 hours. for the following answers, use the normal chart but otherwise be as accurate as possible.
What percentage of snails take more than 60 hours to finish the race?

Could anyone help me figure out how I would go about getting this answer?
• February 19th 2011, 03:33 PM
pickslides
$\displaystyle P(X>60) = P\left( Z> \frac{60 -\mu }{\sigma}\right) = P\left( Z> \frac{60 -50 }{6}\right) = P(Z> 1.67) = \dots$