Question

The formula to find the total surface area of an Rs.5 coin is…………………………….

Answer 1

Hint: Any rupee coin note of what worth it is it always resembles the shape of a cylinder as it has a certain height although the height is very minute that humans eyes usually pays no attention to it, but this fact regarding height proves that a coin is cylindrical in shape.

Complete step-by-step answer:

As we know that the shape of the 5Rs coin is cylinder as shown above.
Now we know in a cylinder there the two circular parts as shown in figure.
And we know that the total surface area (T.S.A) of the cylinder is $2\pi r\left( {h + r} \right)$.
Where r = base radius of the cylinder and h = height of the cylinder.
So the total surface area of the 5Rs coin is $2\pi r\left( {h + r} \right)$.
So this is the required answer.
Hence option (d) is correct.

Note: Whenever we face such types of problems the key is firstly to be known of the conic shape that we are dealing with but after that only the gist of direct formula based approach helps. It is always advisable to keep a good grasp over the formula of conic sections like the curved surface area of cone, cylinder, hemisphere etc.