A solid cone of height 36 cm and radius of base 9 cm is melted to form a solid cylinder of radius 9 cm and height 9 cm. What percent of material is wasted this process?

Height of cone = $$H=36$$ cm and radius of cone = $$R=9$$ cm

=> Volume of cone = $$\frac{1}{3}\pi R^2H$$

= $$\frac{1}{3}\pi (9)^2\times36$$

= $$\pi\times81\times12=972\pi$$ $$cm^3$$

Height of cyinder = $$h=9$$ cm and radius = $$r=9$$ cm

=> Volume of cylinder = $$\pi r^2h$$

= $$\pi\times(9)^2\times9=729\pi$$ $$cm^3$$

$$\therefore$$ % material wasted = $$\frac{(972-729)}{972}\times100$$

= $$\frac{243}{972}\times100=25\%$$

=> Ans - (A)