A shopkeeper buys a radio listed at Rs. 1000 and gets successive discounts of 10% and 20% he spends 10% of the cost price on transportation if he wants a profit of 15%, he should sell the radio for.

Listed price = Rs. 1000. After 10% discount: 1000 × 0.9 = 900. After additional 20% discount: 900 × 0.8 = 720. Transportation cost: 10% of 720 = 72. Total cost = 720 + 72 = 792. For 15% profit: selling price = 792 × 1.15 = 910.80. The key is to apply discounts successively (not additively) and include the transportation cost in the total cost.