Buying and Selling

Cost Price

Cost price is the price at which you buy some product. It is written as CP.

Selling Price

Selling price is the price at which you sell something. It is written as SP.

These are the factors which tell us that the sale of some product is profitable or not.

CP < SPProfitProfit = SP – CP
CP = SPNo profit no loss
CP > SPLossLoss = CP – SP


If the buying price (or CP) of a table is Rs 700 and the selling price (or SP) is Rs 820, then find the profit or loss.


As the SP is more than CP, so the seller earns the profit in the table.

 Profit made = SP – CP 

= Rs 820 – Rs 700

= Rs 80

Profit or loss percentage

The profit and loss can be converted into a percentage. It is always calculated on the cost price.


If the cost price of a laptop is Rs.45000 and the selling price is Rs. 50000, then what is the profit or loss percentage?


How to find SP if CP and profit or loss % is given?


If the cost of a TV is Rs.25000 and shopkeeper sells it at a loss % of 5% then what is the selling price of the TV?


Hence, the shopkeeper sells it at the price of Rs. 23750.

How to find CP if SP and profit or loss % is given?


If the Selling price of a bookshelf is Rs 750 and the profit made by the seller is 10% then what is the cost price of the bookshelf?


Hence the seller bought the bookshelf at the cost of Rs. 682.

Simple Interest

When we borrow some money from the bank then we have to pay some interest to the bank.

The money which we borrow is called the Principal.

The amount which we have to pay to the bank to use that money is called interest.

At the end of the year we return the money to the bank with interest, that money is called Amount.

Amount = Principal + interest


SI = Simple interest

P = Principal

R = Rate of Interest

T = time period


Sunita borrows a loan of Rs 5,0000 at 15% per year as the rate of interest. Find the interest she has to pay at end of one year.


Total amount to be paid by Sunita at the end of one year = Rs.50000 + Rs. 7500 = Rs.57500.

Interest for multiple years

If we have to calculate the interest for more than one year then we have to change the time period only.


In the above example if Sunita takes the loan for 3 years then what will be the total amount after 3 years?


Total amount to be paid by Sunita at the end of 3 years = Rs.50000 + Rs. 22500 = Rs.72500.

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