Various profit and loss formulas used in profit and loss:

1) Generally, profit is calculated as:

                   Profit or gain = Selling price(S.P) - Cost price(C.P)

2) Similarly, Loss =  Cost price - Selling price

3) Gain percentage(%) = Gain * 100

4) Loss percentage(%) = Loss * 100

5) There is a direct relationship between selling price and cost price:

                    S.P.  =  100 + Gain percentage * C.P. (In case of gain)
                    S.P.  =  100 - Loss percentage * C.P. (In case of loss)

For Example :
If an article is sold at gain of 27%, then by using first formula , you can find that S.P. is 127% of C.P.
Similarly, If an article is sold at loss of 18%, then by using second formula , you can find that S.P. is 82% of C.P.

6) If a person sells two commodities at same prices. On one he gains x% and loses x% on another, then as a whole he will be in loss and the loss percentage will be equal to:

       (Common gain or loss percentage)^2  =  x^2
                           100                                            10

Note: Here is an example to find gain in case of dishonesty.

Problem 1: 

A dishonest dealer professes to sell his goods at cost price but he uses a weigh 960 grams for 1 kg. How too calculate gain percentage?

Gain percentage =          Error            * 100 = 40  * 100 (Ans in %)
                                True value - Error            960