Please, I need help fast

Question

Tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation 75 hours. Find the probability that a randomly selected light bulb will last between 675 and 825 hours.

P = [?]%

Hint: Use the 68 - 95 - 99.7 rule.

Answer 1

Pr(675<x<825)= 68%

=Pr(750-75<x<750+75)

=Pr(-z=-1<(x-750)/75<z=+1)

by the empirical rule 68% fall within 1 standard devation from the mean

675 to 825 = 750+/- 75

= 750 plus or minus 1 standard devation from the mean