**Cost Price: **The price at which an article is purchased, is called its cost price, abbreviated as **C.P**

**Selling Price: **The price at which an article is sold is called its **selling price, **abbreviated as **S****.P**

**Profit or Gain: **If S.P is greater than C.P, the seller is said to have a profit or gain

**Loss: ** If S.P is less than C.P., the seller is said to have incurred a loss.

- Gain =(S.P) - (C.P)
- Loss = C.P - S.P
- Loss or gain is always reckoned on C.P
- Gain% = \(\left(\frac{\operatorname{Gain} \times 100}{\mathrm{C.P.}}\right)\)
- Loss% = \(\left(\frac{\operatorname{Loss} \times 100}{\mathrm{C} \cdot \mathrm{P}}\right)\)
- S.P = \(\frac{(100+\operatorname{Gain}\%)}{100} \times \mathrm{C} \cdot \mathrm{P}\)
- S.P = \(\frac{(100-\operatorname{Loss}\%)}{100} \times \mathrm{C} \cdot \mathrm{P}\)
- C.P = \(\frac{100}{(100+\operatorname{Gain}\%)} \times \mathbf{S}.\mathbf{P}\)
- C.P = \(\frac{100}{(100-\operatorname{Loss}\%)} \times \mathbf{S}.\mathbf{P}\)

- If an article is sold at a gain of say, 35 %, then SP = 135% of C.P
- If an article is sold at a loss of say, 35 %, then SP = 65% of C.P
- When a person sells two similar items, one at a gain of say, \(x^{2}\) and the other Loss% = \(\left(\frac{Common\, Loss \,and\, Gain\% }{10}\right) ^{2}\) = \(\left(\frac{x}{10}\right)^{2}\)
- If a trader professes to sell his goods at cost price, bat uses false weights, then Gain% = \(\left[\frac{Error}{(True\,Value)\, -\, (Error) } \times100\right]\) %