A book is sold at three successive discounts of 20%, 20% and 10%. What is 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 20% (on changed price), selling price = $$80-(\frac{20}{100}\times80)$$

= $$80-16=Rs.$$ $$64$$

After 3rd discount of 10%, net selling price = $$64-(\frac{10}{100}\times64)$$

= $$64-6.4=Rs.$$ $$57.6$$

$$\therefore$$ Net discount = $$\frac{(100-57.6)}{100}\times100=42.4\%$$

=> Ans - (A)