The cost price of an article is C.P, the selling price is S.P and the marked price is M.P

• Profit (Loss) = S.P – C.P
• % Profit (Loss) = Profit (Loss)/C.P *100
• Discount = M.P – S.P
• % Discount = Discount/M.P * 100
• Total increase in price due to two subsequent increases of X% and Y% is (X+Y+XY/100)%

The principal amount is P, rate of interest is R and time of loan is T

• Simple Interest = $$\dfrac{P*T*R}{100}$$
• Amount = Principal + Simple Interest
• Compound Interest = $$ P(1+\dfrac{R}{100})^{T}$$ - P
• For the same principal, positive rate of interest and time period, the compound interest on the loan is always greater than the simple interest.

When there are two successive profits of $$x\%$$ and $$y\%$$ then the net percentage profit $$=\ \dfrac{\ x+y+xy}{100}$$.

When there is a profit of $$x\%$$ and loss of $$y\%$$ then net percentage profit or loss $$=\ \dfrac{\ x-y-xy}{100}$$

If an amount 'P' is borrowed for 'n' years at r% per annum compounded annually, and x is the installment that is paid at the end of each year, starting from the first year, then:

$$P\ =\ \dfrac{\ x}{1+\dfrac{r}{100}}+\ \dfrac{\ x}{\left(1+\dfrac{r}{100}\right)^{^2}}+...+\ \dfrac{\ x}{\left(1+\dfrac{r}{100}\right)^{^n}}$$

or 

$$P\ \left(1+\frac{r}{100}\right)^{n\ }=\ x\ \left(\left(1+\frac{r}{100}\right)^{n-1}+\left(1+\frac{r}{100}\right)^{n-2\ }...\ +1\right)$$

A dishonest dealer claims to sell his goods at cost price, but he uses a weight of lesser weight, then the gain% = $$=\ \ \frac{\ true\ weight\ -\ false\ weight}{false\ weight}\times\ 100\%$$

A dishonest dealer sells an item at a profit of x % and uses a weight that is y % less, then the gain%  $$=\ \ \frac{\ \%\ profit\ +\ \%\ less\ in\ weight}{100-\ \%\ less\ in\ weight}\times\ 100\%$$