Explanation
Let's calculate the cost per book:
10 books = 240 rupees, so the cost per book is:
240 rupees ÷ 10 books = 24 rupees per book
To find the cost of 15 books, multiply the cost per book by 15:
24 rupees/book × 15 books = 360 rupees
So, the correct answer is: Rs. 360.