If a man sells a chair for Tk. 600 and he would loss 20%, then at what price should he sell it to gain 20%?

Question: If a man sells a chair for Tk. 600 and he would loss 20%, then at what price should he sell it to gain 20%?

Solution:
Let
the cost price of the chair be x.

Selling price = x - 20% of x
⇒ 600 = x - (20x/100)
⇒ 600 = x - (x/5)
⇒ 600 = 4x/5
⇒ 4x = 3000
∴ x = 750

To gain 20%, the selling price should be = 750 + 20% of 750
= 750 + {(20/100) of 750}
= 750 + 150
= Tk. 900