Samreen sells a keyboard for ₹1,260 at a profit of 25%, and another keyboard for ₹1,440 at a loss of 10%. What is her total gain or loss percentage?

Selling price of the first keyboard = ₹1,260

Profit on the first keyboard = 25%

Selling price of the second keyboard = ₹1,440

Loss on the second keyboard = 10%

Cost Price (CP) with Profit: 

​$$\text{CP} = \frac{\text{SP}}{(1 + \text{Profit Percentage})}$$​​

Cost Price (CP) with Loss:

 ​$$\text{CP} = \frac{\text{SP}}{(1 - \text{Loss Percentage})}$$​​

Total Gain or Loss Percentage:

​$$\text{Total Gain/Loss Percentage} = \frac{\text{Total Profit or Loss}}{\text{Total Cost Price}} \times 100$$​​

For the first keyboard, sold at a 25% profit:

​$$\text{CP}_1 = \frac{1260}{1 + 0.25} = \frac{1260}{1.25} = ₹1,008$$​​

For the second keyboard, sold at a 10% loss:

​$$\text{CP}_2 = \frac{1440}{1 - 0.10} = \frac{1440}{0.90} = ₹1,600$$​​

Total Cost Price:

Total CP = ₹1,008 + ₹1,600 = ₹2,608

Total Selling Price:

Total SP = ₹1,260 + ₹1,440 = ₹2,700

Now,

Profit = Total SP − Total CP = ₹2,700 − ₹2,608 = ₹92

​$$\text{Gain Percentage} = \frac{92}{2608} \times 100 = \frac{575}{163} = \bf 3\frac{86}{163}\%$$​​