DIRECTIONS : Type in your answer in the input box provided below the question. Pavan operates a taco stall outside a shopping mall. On any day, the first 50 tacos that he sells are sold at a price of Rs. 17 per taco. From the 51st taco to the 60th taco that he sells, he sells each taco at a price of Rs. 19. Similarly, for every subsequent batch of 10 tacos that he sells, he increases his selling price by Rs. 2 per taco, as compared to the selling price of the previous batch. Further, it costs Pavan Rs.10 for making each taco. He incurs no other cost in making and selling each taco. The profit that he makes is defined as the total revenue earned from sales minus the total cost incurred. If the average selling price of each taco that Pavan sold on a particular day was more than Rs. 18, what is the minimum number of tacos that he would have sold on that day?

The total revenue for the first 50 tacos is Rs. 850, the next 10 is Rs. 190, the next 10 is Rs. 210, the next 10 is Rs. 230, and the next 10 is Rs. 250. To find the minimum number of tacos for an average selling price above Rs. 18, the total revenue must exceed 18 times the quantity sold. For 70 tacos, the total revenue is Rs. 1730, but 70 times 18 is Rs. 1260 plus the cost of Rs. 10 per taco equals 1260, making the condition valid only after the next batch starts. Testing 73 tacos, we calculate the revenue of the first 70 as Rs. 1730 plus 3 tacos at Rs. 25, which equals Rs. 1805, and since 73 times 18 is Rs. 1314, the average selling price crosses the threshold; however, the actual calculation requires the sum of 850 plus 190, plus 210, plus 230, plus 250 for 70 tacos to be Rs. 1730, and dividing by 70 gives an average of less than 18. Testing 73 tacos gives Rs. 1730 plus 3 at Rs. 25, which is Rs. 1805, so dividing by 73 still does not yield more than Rs. 18, indicating the average condition is met only when the total revenue divided by the count exceeds 18. The minimum number of tacos that satisfies this condition is 73.

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