Explanation:

Correct option 4: i
Given:
i) Two successive discount of 15%
ii) A discount of 20% followed by a discount of 10%
iii) A discount of 30%
solution
 Let the cost price of an item be Rs 100.
For (i), SP after one discount of 15% = 100 - 150 x 100 = Rs 85
SP of first complete discount = 85 - 15% of 85 = 85-15 x 85 /100= Rs 72.25
For (ii), SP after first discount = 100 -20% of 100 = 100-20 = Rs 80
SP of second complete discount = 80-10% of 80 = 80-10 x 80/100 = Rs 72
For (iii), SP after discount of 30% = 100-30% of 100 = 100-30 x100/100= Rs 70
Therefore, under the scheme (i), the selling price is maximum.