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Q.8 Find the cost of polishing a circular table-top of diameter 1.6 m, if the rate of polishing is Rs.15\( m^2. (Take \pi = 3.14) \)
Answer :

Given: Diameter = 1.6 m
\(\therefore Radius = \frac{1.6}{2} = 0.8 m \)
Area of the table-top =\( \pi r^2\)
= 3.14 × 0.8 × 0.8 \(m^2\)
= 2.0096 \(m^2\)
\(\therefore \) Cost of polishing = Rs. 15 × 2.0096
= Rs. 30.144 (approx.)