If three successive discounts of 20%, 30% and 40% are given, then what will be the net discount (in percentage)?

Let marked price = Rs. $$100$$

After 1st discount of 20%, price = $$100-(\frac{20}{100}\times100)$$

= $$100-20=80$$

After 2nd discount of 30% (on changed price), selling price = $$80-(\frac{30}{100}\times80)$$

= $$80-24=Rs.$$ $$56$$

After 3rd discount of 40%, net selling price = $$56-(\frac{40}{100}\times56)$$

= $$56-22.4=Rs.$$ $$33.6$$

$$\therefore$$ Net discount = $$\frac{(100-33.6)}{100}\times100=66.4\%$$

=> Ans - (D)