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?

The sum of the cost prices of A and B is ₹1200.

Let's assume the cost price of A is ₹y.

the cost price of B = ₹(1200-y)

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.

y of (100+10)% + (1200-y) of (100+20)% = 1390

y of 110% + (1200-y) of 120% = 1390

1.1y + 1.2(1200-y) = 1390

1.1y + 1440 - 1.2y = 1390

1440 - 1390 = 1.2y - 1.1y

0.1y = 50

y = 500

Ratio of the cost prices of A and B = y : (1200-y)

= 500 : (1200-500)

= 500 : 700

= 5 : 7