Solution:Let the average cost price of articles ‘A’, ‘B’ and ‘C’ together = Rs. ‘100x’
Then, sum of cost price of all 3 articles = 100x × 3
= Rs. ‘300x’
Average cost price of articles ‘A’ and ‘B’ = Rs. (100x + 100)
Sum of cost price of articles ‘A’ and ‘B’ = (100x + 100) × 2 = Rs. (200x + 200)
So, cost price of article ‘C’ = 300x - 200x - 200
= Rs. (100x - 200)
Let the cost price of article ‘A’ = Rs. ‘Y’
Then, cost price of article ‘B’ = Rs. (Y + 1600)
We have, Y + Y + 1600 = 200x + 200
Or, 2Y + 1600 = 200x + 200
Or, Y = (200x - 1400) ÷ 2 = Rs. (100x - 700)
So, cost price of articles ‘A’ and ‘B’ are Rs. (100x - 700) and Rs. (100x + 900), respectively
Selling price of article ‘A’ = (100x - 700) × 1.25 - 50
= 125x - 875 - 50 = Rs. (125x - 925)
Selling price of article ‘C’ = (100x - 200) × 1.2 - 360
= 120x - 240 - 360 = Rs. (120x - 600)
According to the question,
(125x - 925) : (120x - 600) = 11 : 12
Or, 1500x - 11100 = 1320x - 6600
Or, 180x = 4500
So, x = 25
And, cost price of article ‘B’ = 100x + 900
= Rs. 3,400
So, required selling price of article ‘B’ = 3400 × 1.15
= Rs. 3,910