Question

find the total surface area of cone if its slant heigh is 21 m and diameter of its base is 24 m

Answer 1

diameter=24m.
therefore radius=12m.
slant height(l)=21m.
thus total surface area of the cone=pi(r)(l+r).  
=22/7(12)(21+12).  
=22/7(12)(33)  
=1244.57m 

Answer 2

hi dear

total surface area of cone =
$\pi \: rl + \pi {r}^{2}$
diameter =24=2*radius
so radius =24/2=12
slant height =21
putting values in formula,,,
=(22/7*12*21)+(22/7*12*12)
=22/7(12*21+12*12)
=22/7(252+144)
=22/7(396)
=1244.5 meter square