Solution:Let the sum of cost price of articles ‘A’, ‘B’ and ‘C’ = Rs. ‘60x’
Then, average cost price of articles ‘A’, ‘B’ and ‘C’
= 60x ÷ 3 = Rs. ‘20x’
Average cost price of articles ‘B’ and ‘C’ = 20x × 1.15 = Rs. ‘23x’
And, sum of cost price of articles ‘B’ and ‘C’ = 23x × 2 = Rs. ‘46x’
So, cost price of article ‘A’ = 60x - 46x = Rs. ‘14x’
Let the cost price of article ‘B’ = Rs. ‘y’
Then, cost price of article ‘C’ = Rs. (y + 600)
So, y + y + 600 = 46x
Or, 2y + 600 = 46x
So, y = (46x - 600) ÷ 2 = (23x - 300)
So, cost price of articles ‘B’ and ‘C’ are Rs. (23x - 300) and Rs. (23x + 300), respectively
According to the question,
14x × 1.4 + (23x - 300) × 0.85 - (14x + 23x - 300)
= 14x × 1.4 + (23x + 300) × 0.7 - (14x + 23x + 300) + 480
Or, 19.6x + 19.55x - 255 - 37x + 300 = 19.6x + 16.1x + 210 - 37x - 300 + 480
Or, 2.15x + 45 = 390 - 1.3x
Or, 3.45x = 390 - 45 = 345
So, x = 345 ÷ 3.45 = 100
So, cost price of articles ‘A’, ‘B’ and ‘C’ are Rs. 1,400, Rs. 2,000 and Rs. 2,600, respectively.
So, cost price of article ‘C’ = Rs. 2,600