Curved surface area of cylinder
2πrh=π×8×10=80×π
The slant height of frustum can be calculated as follows:
l=√h2+(r1−r2)2=√122+(9−4)2=√144+25=√169=13 cm
Curved surface area of frustum
=π(r1+r2)l=π(9+4)×13=169π
Total curved surface area
=169π+80π=249×3.14=781.86 cm2