Question

Sebuah kerucut mempunyai luas selimut 220 cm (pngkt 2) jika pnjang garis plukisnya 14 cm. tentukan:
A. panjang jari-jari
b. tinggi kerucut
c. volume kerucut

Answer 1

Luas selimut = 220 cm ^2
s = 14 cm
a) luas selimut = phi x r x s
   220 = 3,14 x r x 14
220 = 43,96 x r
r = 220 / 43,96
r = 5 cm
b) t^2 = s^2 - r^2
   t^2 = 14^2 - 5^2
   t^2 = 196 - 25
   t^2 = 171
   t = akar 171
   t = 13 cm
c) v kerucut = 1/3 x phi x r^2 x t
= 1/3 x 3,14 x 5^2 x 13
= 1/3 x 3,14 x 25 x 13
= 340 cm ^3

Answer 2

Lsk = 220
πrs = 220
22/7xrx14 = 220
44 r  =220
r = 220/44
r = 5

t² = s²-r²
   =14²-5²
   =196=25
t²=171
t=√171
t=13,07

vk= 1/3 πr²t
    =1/3 x3,14x5x5x13,07
    =341,99