A right angled triangle whose sides are 3 cm, 4 cm and 5 cm is revolved about the sides containing the right angle in two ways. Find the difference in volumes of the two cones so formed. Also, find their curved surfaces.
Height of the cone (h1)=3 cm
Radius of the cone (r1) = 4 cm
Slant height of the cone (l1) = 5 cm
Volume of cone (V1)= 
cm3
cm3
Again after rotating
Height of the cone (h2)=4 cm
Radius of the cone (r2)=3 cm
Slant height of the cone (l2)=5 cm
Volume of cone (V2)
cm3
cm3
Difference between the volume two cones =16π – 12π
= 4π cm3
Curved surface area of first cone =π × r1× l1
= π × 4 × 5
= 20
cm2
Curved surface area of second cone 
= 15
cm2
38