Question

There is a cylinder of base radius 3 cm and length 10 cm. Ram attaches a hemispherical attachment to each flat end of the cylinder having the same radius as the base radius of the cylinder. What is the surface area of the combined solid in $c{m}^2$ ?

• A. 201
• B. 302
• C. 310
• D. 400

Answer 1

The correct option is B

302

Now let us visualise the combined solid.

It can be seen clearly how 2 hemispheres are attached to a cylinder. It is clear that the surface area of the combined solid is just the sum of the curved surface areas of the cylinder and the hemispheres.

Hence T.S.A of solid = 2(C.S.A of hemisphere) + C.S.A of cylinder

= 2(2$\pi$$r^2$) + 2$\pi$rh

= 4$\pi$$(3{)}^2$ + 2$\pi$(3)(10)

= 302 $c{m}^2$ (approx)