960 yuan, a bookstore, bought 40 books and found that 10 books were damaged. The shopkeeper sold these complete books at a price of 67.2 yuan each. What is the profit margin of these books?
The cost of each book is 960/40 = 24 yuan.
The profitability of intact books is (67.2-24)/24x100% =180%.
The price of each damaged book is 24-24x20%= 19.2 yuan.
After all these books (40 books) are sold, the profitability is (67.2x30+19.2x10-960) ÷ 960x100% =130%.