Question

The average price of 18 books is Rs.15 while the average price of 15 of these books is Rs.13. Of the remaining three books, if the price of one book is 50% more and the price of the second book is 50% less than the third book, then what is the price of the cheapest book?

• A. 15
• B. 10
• C. 12.5
• D. 12

Answer 1

The correct option is C 12.5

Total cost of the 18 books $=18\times 15=270$
Total cost of the 15 books with average cost $13=15\times 13=195$
Total cost of the last 3 books $=270-195=75$
Now, the prices of the 3 books are $\to$ 0.5x, x and 1.5x
Therefore x+0.5x+1.5x=3x=75
Price of the cheapest book, 0.5x $=\frac{75}{6}=12.5$ Rs.