The ages of rocks in an isolated area are known to be approximately normally distributed with a mean of 7 years and a standard deviation of 1.8 years. What percent of rocks are between 5.8 and 7.3 years old?

31.39%

Step-by-step explanation:

Given: The ages of rocks in an isolated area are known to be approximately normally distributed with a mean of 7 years and a standard deviation of 1.8 years.

i.e.

Let X be the age of rocks in an isolated area .

Then, the probability that rocks are between 5.8 and 7.3 years old :

Hence, the percent of rocks are between 5.8 and 7.3 years old = 31.39%

a. is correct

step-by-step explanation:

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