laboratory tests show that the lives of light bulbs are normally distributed with a mean of 750 hours and a standard deviation of 75 hours. find the probability that a randomly selected light bulb will last between 825 and 900 hours.

0.13591

Step-by-step explanation:

What we do here is find a score of both values;

Mathematically;

z-score = (x - mean)/SD

for 825, we have (825-750)/75 = 1

For 900, we have (900-750)/75 = 150/75 = 2

So the probability we want to find is;

P(1<x<2) = P(x<2) - P(x<1)

We use the standard table for this and we arrive at;

P(1<x<2) = 0.13591

4a. is 3 miles every hour

4b. is 1/3 of an hour per mile

step-by-step explanation: