The core formulas for percentage, profit, loss and discount, with five worked money problems of the kind that appear in exams.
Formulas to memorise
- Profit = SP − CP | Loss = CP − SP
- Profit% = (Profit / CP) × 100 | Loss% = (Loss / CP) × 100
- Discount = Marked Price − Selling Price
(CP = cost price, SP = selling price.)
Worked examples
- A pen bought for Rs. 40 is sold for Rs. 50. Profit = 10, Profit% = (10/40)×100 = 25%.
- A bag costing Rs. 800 is sold at a 15% loss. Loss = 15% of 800 = 120, so SP = Rs. 680.
- Find 18% of 250: (18/100)×250 = 45.
- A shirt marked Rs. 1200 has a 20% discount. Discount = 240, so you pay Rs. 960.
- An item sold for Rs. 660 at 10% profit. CP = 660 / 1.10 = Rs. 600.
Exam tip: Profit% and Loss% are always calculated on the cost price, never the selling price.