A person who plans to sell his old laptop for Rs 4800 will lose 20%. To get a profit of 15%, he should sell it at the following:

Formula Used:

Profit % = Profit/Cost price × 100

Profit = Selling price - Cost price  

Loss%  = Loss/Cost price × 100

Loss = Cost price - Selling price 

Calculation:

Let the Cost price of the laptop be Rs.

ATQ: 20 = (x - 4800)/x × 100

⇒ 20x = 100x - 480000

⇒ 80x = 480000

⇒ x = 6000

For 15% Profit,

Let selling price be .

⇒ 15 = (y - 6000)/6000 × 100

⇒ 15 = (y - 6000)/60

⇒ y - 6000 = 900

⇒ y = 6900

Hence, he needs to sell his laptop of Rs. 6900 for 15% profit.

Shortcut TrickLoss% = 20% = 1/5 = If C.P. = 5 units then 1 unit loss. So, S.P. = 4 units.

⇒ 4 units = Rs. 4800 (given)

⇒ 5 units i.e. C.P  = 5 × 1200 = Rs. 6000

Now, the profit amount = 15% of 6000 = Rs. 900

Hence, the required S.P. = Rs. 6000 + Rs.900 = Rs. 6900