A certain brand of refrigerator has a useful life that is normally distributed with mean 10 years and standard deviation 3 years. The useful lives of these refrigerators are independent. Calculate the probability that the total useful life of two randomly selected refrigerators will exceed 1.9 times the useful life of a third randomly selected refrigerator.

0.55567

Step-by-step explanation:

Given : A certain brand of refrigerator has a useful life that is normally distributed with mean 10 years and standard deviation 3 years. The useful lives of these refrigerators are independent.

i.e.

Let and are two randomly selected refrigerator's life whose sum will exceed third selected refrigerator .

So that,

Mean

Standard deviation =

Z-score :

Now , The  probability that the total useful life of two(i..e n=2) randomly selected refrigerators will exceed 1.9 times the useful life of a third randomly selected refrigerator would be :-

Hence, the required probability is 0.55567.

answer:

a=9

step-by-step explanation: lmk if you need a explanation

step-by-step explanation:

(3rd option) - c