# The cost price of a copy is :

12 copies of a book were sold for 1800, thereby gaining the cost price of 3 copies. The cost price of a copy is

- Rs. 120
- Rs. 150
- Rs. 1200
- Rs. 1500

**Answer: (1) Rs. 120 **

**Explanation:-**

Let the cost price of a book be Rs. X

Therefore, the cost price of 3 books = Rs. 3 X

And, the cost price of 12 books = Rs. 12 X

Selling price of 12 books = Rs. 1800

Then, 12 X + 3 X = 1800

15 X = 1800

X = 1800/15

X = 120

Then, the cost price of a book is Rs. 120.

Hence, the correct answer is option (1) Rs. 120.