A man buys a dog and a sheep for Rs. 4500. He sells the dog at a profit of 20% and the sheep at a profit of 5%. Find the cost price of the dog, if his overall profit on both the bargains is 17.5%.

Let dog cost = d, so sheep cost = 4500-d. Dog sold at 20% profit: 1.2d. Sheep sold at 5% profit: 1.05(4500-d) = 4725 - 1.05d. Total selling price = 1.2d + 4725 - 1.05d = 4725 + 0.15d. Overall profit is 17.5%, so total SP = 1.175 × 4500 = 5287.5. Setting 4725 + 0.15d = 5287.5 gives 0.15d = 562.5, so d = 3750. Verification: Dog SP = 4500, Sheep SP = 787.5, Total = 5287.5 (17.5% of 4500).