Effective Discount (ED)=d1+d2−(d1×d2)∕100 Where, d 1 and d 2 are the successive discount percentages. Calculations: For I: ⇒ED=20+20−(20×20)∕100 ⇒ED=40−4=36% For II: ⇒ED=25+15−(25×15)∕100 ⇒ED=40−3.75=36.25% For III: ⇒ED=30+10−(30×10)∕100 ⇒ED=40−3=37% For IV: ⇒ED=5+35−(5×35)∕100 ⇒ED=40−1.75=38.25%