Rule  Description 

1  If S.P. > C.P. then there will be profit.
Note: Both profit and loss are always calculated on cost price only. 
2  If C.P. > S.P. then there will be profit.

3  If an object is sold on r% Profit, then

4  If an object is sold on r% loss, then

5  If A sells an article to B at a% profit and B sells it to C at b% profit (OR) If a% and b% are two successive profits, then Total Profit % = \[\left(a+b+\frac{ab}{100}\right)\%\] 
6  If A sells an article to B at a% profit and B sells it to C at b% profit and if C paid x, then amount paid by A will be \[A=x\times\left(\frac{100}{100+a}\right)\left(\frac{100}{100+b}\right)\] 
7  If a% and b% are two successive losses, then Total Loss % = \[\left(ab+\frac{ab}{100}\right)\%\] 
8  If a% profit and b% loss occur, simultaneously, then overall loss or profit% is \[\left(ab\frac{ab}{100}\right)\%\] 
9  If a% loss and b% profit occur, simultaneously then overall loss or profit% is \[\left(ab\frac{ab}{100}\right)\%\] 
10  If a% loss and b% profit occur, simultaneously then overall loss or profit% is \[\left(ab\frac{ab}{100}\right)\%\] 
11  If a% loss and b% profit occur then, total loss/profit is \[\left(a+b\frac{ab}{100}\right)\%\] 
12  If cost price of ‘x’ articles is equal to selling price of ‘y’ articles, then Selling Price = x, Cost Price = y Hence, Profit or Loss % = \[\frac{xy}{y} \times 100\] 
13  On selling ‘x’ articles the profit or loss is equal to Selling of ‘y’ articles, then

14  If a man sells two similar objects, one at a loss of x% and another at a gain of x%, then he always incurs loss in this transaction and loss % = \[\frac{x^2}{100} \%\] 
15  A man sells his items at a profit/loss of x%. If he had sold it for R more, he would have gained/lost y%. Then C.P. of items = \[\frac{R}{\left(y\pm x\right)}\times100\]

16  If a man purchases ‘a’ items for x and sells ‘b’ items for y. then profit or loss per cent is given by \[\left(\frac{aybx}{bx}\right)\times100\%\] 
17  If the total cost of ‘a’ articles having equal cost is x and the total selling price of ‘b’ articles is y, then in the transaction gain or loss per cent is given by \[\left(\frac{aybx}{bx}\right)\times100\%\] 
18  A dishonest shopkeeper sells his goods at C.P. but uses false weight, then Gain % = \[\left(\frac{\text{True weight  False weight}}{\text{False weight}}\right)\times100\] (OR) Gain % = \[\left(\frac{\text{Error}}{\text{True value  Error}}\right)\times100\] 
19  If A sells an article to B at a profit (loss) of r_{1}% and B sells the same article to C at a profit (loss) of r_{2}% then the cost price of article for C will be given by C.P of article for C = \[\text{C.P. of A} \times\left(1\pm\frac{r_1}{100}\right)\left(1\pm\frac{r_2}{100}\right)\] (Positive and negative sign conventions are used for profit and loss.) 
20  If a vendor used to sell his articles at x% loss on cost price but uses y grams instead of z grams, then his profit or loss% is \[\left[\left(100x\right)\frac{z}{y}100\right]\%\] (Profit or loss as per positive or negative sign). 