Question

7
'The radius of a circular brass places 20 find the cost of polishing, the cap
12, such plates at the rate of 450, per sq.
$(take \pi = 3.14)$
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Answer 1

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

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