Let the marked price of an article be Rs.100
Then first discount on it =Rs.20
Price after discount =Rs.(100−20)=Rs.80
Second discount on it =10% of Rs.80
Rs.(80×10100)=Rs.8
Price after second discount =Rs.(80−8)=Rs.72
Net selling price =Rs.72
Single discount equivalent to given successive discounts =(100−72)=28%