Question

11. 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 3450 per sq. m.
(Take it = 3.14)​

Answer 1

Answer:

Total area to be polished = 12 × 0.1256 = 1.5072 m². Total cost of polishing = Polishing rate × Total area.

Answer 2

Answer:

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

Step-by-step explanation: