Solution -
If the total sale price of these two articles is Rs. 30,000.
There is no loss or gain.
So,
Total Cost price = Total sale price = 30,000
Let,
C.P of first article = x
S.P of first article = 0.9x ___________ (1)
C.P of second article = 30,000 - x
S.P of second article = (30,000 - x)1.15
= 34,500 - 1.15x ____________ (2)
The S.P of both articles = Rs. 30,000
So,
0.9x + 34,500 - 1.15x = 30,000
- 0.25x = 30,000 - 34,500
- 0.25x = - 4,500
0.25x = 4,500
x = 4,500 / 0.25
x = 18000
C.P of first article = x
C.P of first article = 18,000
C.P of second article = 30,000 - x
C.P of second article = 30,000 - 18000
C.P of second article = 12,000
Therefore,
The difference between their cost prices = 18,000 - 12,000
= 6,000
Hence,
The correct answer is (b) Rs. 6000.
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