Question

A sphere has the same curved surface as the total surface area of cylinder of height 4 cm and diameter of base 8 cm. The radius of the sphere is

• A. $2cm$
• B. $3cm$
• C. $4cm$
• D. $6cm$

Answer 1

The correct option is C $4cm$

Let the radius of the sphere be $r$. Then curved surface of sphere $=4\pi r^2$
Total surface of cylinder
$=2\pi .r.(r+h)$
$=2\pi \times 4\times (4+4)=64\pi$
$\therefore 4\pi r^2=64\pi$
$\therefore r=4$ cm