# What will be Cost Price of Copy? If

12 copies of a book were sold for Rs.1800 there by gaining cost price of 3 copies. Then the cost price of a copy is

- Rs.120
- Rs.150
- Rs.1,200
- Rs.1,500

**Answer: (a) Rs. 120
Explanation:-
**Let be the cost price of 1 copy = Rs. X

Cost price of 3 copies =Rs. 3X

Cost price of 12 copies =Rs. 12X

Selling price of 12 copies =Rs. 1800

12X + 3X = 1800

15X = 1800

X = 1800/15

X = 120