A Major Department Store Has Determined That Its Customers Charge

Short Answer

A major department store has determined that its customers charge an average of $500 per month, with a standard deviation of $80. Assume the amounts of charges are normally distributed.
a.What percentage of customers charges more than $380 per month?
b.What percentage of customers charges less than $340 per month?
c.What percentage of customers charges between $644 and $700 per month?