The average price, or the expected price, of any item in this specialty store is given by the weighted average of each item's price. That is, the sum of the products of each individual price by its corresponding sales mix:
The average price of any item in the store is $7.28
There are 10 feet of posts on each side. That means there are 40 feet of fencing in total. If you divide that by two (to represent posts being 2 feet apart) then you get 20. There are 20 posts needed.
