### Theory:

1. If the cost price is lesser than the selling price, then there is a profit.

$$\text{Profit}$$ $$=$$ $$\text{S.P.}$$ $$-$$ $$\text{C.P.}$$

2. If the selling price is lesser than the cost price, then there is a loss.

$$\text{Loss}$$ $$=$$ $$\text{C.P.}$$ $$-$$ $$\text{S.P.}$$

3. If the cost price equals the selling price, then there is neither profit nor loss.

$$\text{C.P.}$$ $$=$$ $$\text{S.P.}$$ (Neither profit nor loss)

4. $$\text{Discount}$$ $$=$$ $$\text{M.P.}$$ $$-$$ $$\text{S.P.}$$ (or) $$\text{S.P.}$$ $$=$$ $$\text{M.P.}$$ $$-$$ $$\text{Discount}$$

5. If there is no discount, then $$\text{M.P.}$$ $$=$$ $$\text{S.P.}$$
Example:
1. If C.P. $$= Rs.1200$$, S.P. $$= Rs.1500$$, find profit or loss.

In this case, S.P. $$>$$ C.P.

$$\text{Profit}$$ $$=$$ $$\text{S.P.}$$ $$-$$ $$\text{C.P.}$$

$$=$$ $$1500$$ $$-$$ $$1200$$ $$= Rs.300$$

Profit $$= Rs.300$$

2. If C.P. $$= Rs.2000$$, S.P. $$= Rs.1000$$, find profit or loss.

In this case, C.P. $$>$$ S.P.

$$\text{Loss}$$ $$=$$ $$\text{C.P.}$$ $$-$$ $$\text{S.P.}$$

$$2000 - 1000$$ $$=$$ $$Rs.$$$$1000$$

Loss $$=$$ $$Rs.$$$$1000$$

3. If C.P. $$= Rs.2200$$, S.P. $$= Rs.2200$$, find profit or loss.

In this case, $$\text{C.P.}$$ $$=$$ $$\text{S.P.}$$

Therefore, there is neither profit nor loss.

4. If the M.P. $$= Rs.10000$$, S.P. $$= Rs.9000$$, find discount.

$$\text{Discount}$$ $$=$$ $$\text{M.P.}$$ $$-$$ $$\text{S.P.}$$

$$= 10000 - 9000$$

$$= Rs.1000$$

5. If M.P. $$=$$ $$Rs.1550$$, Discount $$= Rs.250$$, find S.P.

$$\text{S.P.}$$ $$=$$ $$\text{M.P.}$$ $$-$$ $$\text{Discount}$$

$$= 1550 - 250$$

$$= Rs.1300$$

6. If M.P. $$= Rs.200$$, S.P. $$= Rs.200$$, find discount.

In this case, $$\text{M.P.}$$ $$=$$ $$\text{S.P.}$$

So, there is no discount.