4. A laptop and a mobile phone were bought for 40000 and 24000 respective

shopkeeper made a profit of 8% on laptop and a loss of 12% on mobile phone to find

his gain or loss percent on the whole transaction.

His gain is 0.5%

Step-by-step explanation:

* Lets explain how to solve the problem

- The price of the laptop is 40000

- The profit on laptop is 8%

∵ Profit = Cost price * percentage of the profit

∵ Cost price = 40000

∵ Percentage of the profit = 8%

∴ Profit = 40000 * 8/100 = 3200

- The price of the mobile phone is 24000

- The loss on mobile phone is 12%

∵ Loss = Cost price * percentage of the loss

∵ Cost price = 24000

∵ Percentage of the loss = 12%

∴ Loss = 24000 * 12/100 = 2880

- Lets calculate the selling price of the laptop

∵ The selling price of the laptop = cost price + profit

∵ Cost price is 40000 and profit is 3200

∴ the selling price of laptop = 40000 + 3200 = 43200

- Lets calculate the selling price of the mobile phone

∵ The selling price of the mobile phone = cost price - loss

∵ Cost price is 24000 and loss is 2880

∴ the selling price of mobile phone = 24000 - 2880 = 21120

- Now lets find the total cost and the total selling prices

∵ The total cost = the cost of laptop + cost of mobile phone

∵ The cost of laptop is 40000 and the cost of mobile phone is 24000

∴ The total cost price = 40000 + 24000 = 64000

∵ The selling price of laptop is 43200 and the selling price of mobile

phone is 21120

∴ The total selling price = 43200 + 21120 = 64320

- If the selling price is greater than the cost price, then he's gain but

If the selling price is smaller than the cost price, then he's loss

∵ The selling price is 64320 and the cost price is 64000

∴ The selling price > cost price

∴ He is gain

∵ The gain % = (gain : cost price) * 100%

∵ The gain = 64320 - 64000 = 320

∴ The gain % = (320 : 64000) * 100% = 0.5%

* His gain is 0.5%