Sita purchased 10 books, 15 diaries, and 20 folders for

Solution

According to the question Let the cost price of each book, each diary, and each folder be Rs. ‘z’ Selling price of each book = (500/10) = Rs. 50 Selling price of each diary = (1200/15) = Rs. 80 According to the question, (50–z)/z×100 = e…… (I) Also, (80–z)/z×100 = f…… (II) Use the given relationship [f = 3e] Dividing equation (I) by (II), we get 3(50 − z)=80 − z 150 − 3z = 80 − z 150 − 80 = 3z − z 70 = 2z z = (70/2) = 35 Cost Price of All Folders: Cost price of one folder = Rs. 35 Cost price of all 20 folders = Rs. 35 × 20 = 700 Calculate the Profit Earned on Selling All Folders: Selling price of all 20 folders = Rs. 1000 Profit = Selling price - Cost price = Rs.1000 − 700 = 300 The profit earned by the seller on selling all the folders is Rs. 300.