The sum of the cost prices of A and B is ₹1200, The sum of the selling prices of A and B is ₹1390. If the profits earned on A and B are 10% and 20%. respectively, then what is the ratio of the cost prices of A and B?

5 : 7

Let the cost price of A be x

The cost price of B = 1200 - x

x × 110% + (1200 - x) × 120% = 1390

1440 - 10x % = 1390

10 × x% = 50

x = 500

Cost price of A = x = Rs. 500

Cost price of B = 1200 - x = Rs. 700

Cost price of A : Cost price of B = 500 : 700 = 5 : 7