Question

Jika alas sebuah kerucut memiliki panjang jari-jari alas 5 cm dan luas selimut 220 cm2 , maka tentukan volume kerucut tersebut !

Answer 1

Luas selimut kerucut = phi x R x s
220 = 22/7 x 5 x s
220 = 110/7 x s
s = 220 : 110/7
s = 220 x 7/110
s = 2 x 7
s = 14 cm

t^2 = s^2 - R^2 (^=pangkat)
t^2 = 14^2 - 5^2
t^2 = 196 - 25
t^2 = 144
t = akar 144
t = 12

volume kerucut = 1/3 x phi x R^2 x t
= 1/3 x 3,14 x 5^2 x 12
= 1/3 x 12 x 3,14 x 25
= 4 x 25 x 3,14
= 100 x 3,14
= 314 cm^3

Answer 2

(1) Cari panjang selimut dan tinggi
L.Selimut= phi.r.s
220=22/7.5.s
s=220/22/7.5
s=14

t^2=s^2-r^2
t^2=14^2-5^2
t^2=196-25
t^2=171
t=13,07 --> 13

(2) Cari volume kerucut
V=1/3.phi.r^2.t
V=1/3.3,14.5^2.13
V=1/3.78,5.13
V=1/3.1020,5
V=340,166