Question

radii of circular ends of a frustum of cone are 1 cm and 4 cm its height is 10 cm It is melted to form a solid cylinder of height 5 cm then radius of cylinder is​

Answer 1

Answer:

753.6cm

Step-by-step explanation:

Curved Surface area of a frustum of a cone  =πl(r1+r2), where l is the slant height 

l=h2+(r1−r2)2, where h is the height, r1 and r2 are the radii of the lower and upper ends of a frustum of a cone.

So, 

l=92+(14−12)2 =85 cm

Hence, Curved Surface area of this frustum of a cone =3.14×85×(14+12) cm2

                                                                                           =753.6 cm