Question

$\text{A cone is 8.4 cm high and the radius of its base is 2.1 cm.It is melted and recast into a sphere. The radius of the sphere is}\left(a\right)4.2cm\left(b\right)2.1cm\left(c\right)2.4cm\left(d\right)1.6cm$

Answer 1

Radius of cone = $\frac{1}{3}\pi r^{2}h$
=$\frac{1}{3}\times \frac{22}{7}\times 2.1\times 2.1\times 8.4$
= 38.808 cm³
volume of sphere = volume of cone
$\frac{4}{3}\pi r^3=38.808$
$r^3=9.261$
$r=2.1cm$

Ans-b