**Important Terms and Formulas**

**1. Cost Price (C.P.):-** The price at which an article is purchased is called its cost price.

**2. Selling Price (S.P.):-** The price at which an article is sold is called its selling price.

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

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

**5. Gain or Loss % **is always calculated on C.P.

**6. Gain %** = ${(\frac{Gain\times 100}{C.P})}$

**7. Loss %** = ${(\frac{Loss\times 100}{C.P})}$

8. S.P = ${\begin{bmatrix}\frac{(100 +Gain\%)}{100}\times C.P \end{bmatrix}}$

**9. S.P** = ${\begin{bmatrix}\frac{(100 â€“ Loss\%)}{100}\times C.P \end{bmatrix}}$

**10. C.P** = ${\begin{bmatrix}\frac{100}{(100+Gain\%)}\times S.P \end{bmatrix}}$

**11. C.P** = ${\begin{bmatrix}\frac{100}{(100- Loss\%)}\times S.P \end{bmatrix}}$

**12.** If an article is sold at a gain of 30% then S.P = 130% of C.P

**13.** If an article is sold at a loss of 10% then S.P =90% of C.P

**14.** If a trader professes to sell his goods at cost price, but uses false weights, then % Gain = ${\frac{Error}{True\quad value - Error}\times 100}$