A bookseller procures 40 books for Rs. 3200 and sells them at a profit equal to the selling price of 8 books. What is the selling price of one dozen books, if the price of each book is same?

Explanation:-

Cost price of each book,
= ³²⁰⁰/₄₀ = Rs. 80.
Now,
Selling Price of 40 books = CP of 40 books + SP of 8 books.
Selling Price of 40 books - SP of 8 books = CP of 40 books.
SP of 32 books = Rs. 3200
SP of 1 book = ³²⁰⁰/₃₂ = Rs. 100.
So, Selling price of one dozen (12) book = 12*100 = Rs. 1200.