Since the radius of the semi circle is 10 cm then the diameter is 20 cm, when folded, its circumference is now 20, given the circumference find the radius of the cone. i guess
Volume = 1/3 πr2 (l2﹣r2)1/2
circumference = 20 cm = πD
D=6.363636364
Radius = 6.363636364/2 = 3.181818182
l = 10
vol = 100.51cm3
curved s.a = πrl
=99.96cm2
