How to compute for gain and loss?

Question
The selling price of 10 articles is equal to cost price of 11 articles. Find the gain or loss per cent.




Solution
Let P = selling price
C = cost

Therefore, the above word problem is translated to the following equation
10P = 11C
Isolating P results to
P = 1.1C

Gain or loss, in percentage, is calculated by
P-C
----x100%
C

Therefore,

1.1C - C
--------x 100%
C

Therefore the gain is 10%

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