A circular grassy plot of land, 42 cm is diameter, has a path 3.5 m wide running around it outside. The cost of gravelling the path at Rs. 4 per square metre is :
Options:
A . Rs. 1002
B . Rs. 1802
C . Rs. 2002
D . Rs. 3002
Answer: Option C Radius of the plot = 21 m Area of the path : $$\eqalign{ & = \pi \left[ {{{\left( {24.5} \right)}^2} - {{\left( {21} \right)}^2}} \right]{m^2} \cr & = \left[ {\pi \left( {24.5 + 21} \right)\left( {24.5 - 21} \right)} \right]{m^2} \cr & = \left( {\frac{{22}}{7} \times 45.5 \times 3.5} \right){m^2} \cr & = 500.5\,{m^2} \cr} $$ ∴ Cost of gravelling : = Rs. (500.5 × 4) = Rs. 2002
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