CAT 2019 Slot 1 — QA Question 22
Percentage ChangeEasy
On selling a pen at 5% loss and a book at 15% gain, Karim gains Rs. 7. If he sells the pen at 5% gain and the book at 10% gain, he gains Rs. 13. What is the cost price of the book in Rupees?
Answer & solution
- A
95
- B
85
- C
100
80
Solution
Let the cost price of one pen and one book be 100p and 100b respectively.
On selling a pen at 5% loss and a book at 15% gain, Karim gains Rs. 7.
∴ 95p + 115b = 7 + (100p + 100b) ⇒ 15b − 5p = 7 ...(1)
On selling the pen at 5% gain and the book at 10% gain, he gains Rs. 13.
∴ 105p + 110b = 13 + (100p + 100b) ⇒ 10b + 5p = 13 ...(2)
Solving (1) and (2), we get; b = 4/5.
So, cost price of one book = 100b = 100 × (4/5) = Rs. 80.
Hence, option (d).