How many of the 250 perch netted by a fisherman would you expect to have a mass more than 400g if the mass of the perch are normally distributed with a mean of 300g and a standard deviation of 80g.
Entering the data into the applet at
http://davidmlane.com/hyperstat/z_table.html
gave me a prob of .10565
so of the 250 perch
appr. (250)(.10565) or 26 perch would be over 400 g