Question

Steel rods are manufactured with a mean length of 21 centimeter​ (cm). Because of variability in the manufacturing​ process, the lengths of the rods are approximately normally distributed with a standard deviation of 0.09 cm. Complete parts ​(a) to ​(d). ​

(a) What proportion of rods has a length less than 20.9 ​cm?

​(b) Any rods that are shorter than 20.81 cm or longer than 21.19 cm are discarded. What proportion of rods will be​ discarded?

​(c) Using the results of part ​(b)​, if 5000 rods are manufactured in a​ day, how many should the plant manager expect to​ discard?

Answer 1