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The radius of a circular brass plate is 20 cm. Find the cost of polishing the top surface of 12 such plates at the rate of Rs 450 per sq. m. (take pi 3.14)

Let the radius of the circular brass plate = r = 20 cm = 1/5 m Polishing rate = 450 rupees/m² Total area of brass plate = Area of the circle, whose radius is 1/5 m = πr² = 3.14 × (1/5)² Total area of a brass plate = 0.1256 m² since we have 12 identical brass plat. Total area to be Polished = 12(Area of one brass plate) Total area to be polished = 12 × 0.1256 = 1.5072 m². Total cost of polishing = Polishing rate × Total area. There total cost of polishing = 450 × 1.5072 = 678.25 rupees