Question

1. The weight of a certain type of brick has an expectation of 1.12kg with a standard deviation of 0.03kg.
(a) What are the expectation and variance of the average weight of 25 bricks randomly selected?
(b) How many bricks need to be selected so that their average weight has a standard deviation of no
more than 0.005kg?

Answer 1

You'll have to get the variance for 1 brick and multiply by 25. From the variance you can use a calculator to get the expectation

Answer 2

You know how to get the variance for 1 brick?