Question

A flower pot is in the form of a hollow cylinder with a closed base with inner radius $2cm$ and outer radius $4cm$ . The height of the flower pot is $10cm$ . If the pot has to be polished find the cost of polishing if the cost of polishing per ${cm}^2$ is $Rs.2$.

• A. $Rs.276.32$
• B. $Rs.275$
• C. $Rs.270$
• D. $Rs.278.64$

Answer 1

The correct option is A $Rs.276.32$

We have to first find the total surface area of the flower pot.
Outer radius $=4cm$
Inner radius $=2cm$
Height of flower pot $=10cm$
Total surface area $=A=2\pi Rh+2\pi rh+\pi R^2+\pi r^2$
$A=2\pi (R+r)h+\pi (R^2+r^2)A=2\pi (4+2)2+\pi (16+4)A=24\pi +20\pi =44\pi A=40\pi =44\times 3.14=138.16{cm}^2$
Cost of fabrication per ${cm}^2$ $=Rs.2$
Total cost of fabrication $==138.16\times 2=Rs.276.32$