Question

1. tentukan tinggi kerucut ini =
v= 300π, r=10m
2. tentukan jari jari kerucut ini =
v= 120π, t=10
3. tentukan tinggi kerucut ini =
a. l=225π , s=16
b. v = 150π , d =15
c. l = 180π , d = 16

Answer 1

1)
V kerucut = 300 phi
1/3.phi.r².t = 300 phi
1/3.phi.10².t = 300 phi
1/3.100.t = 300
100/3 . t = 300
t = 300 : 100/3
t = 300 . 3/100
t = 3.3
t = 9 m


2)
V kerucut = 120 phi
1/3.phi.r².t = 120 phi
1/3.phi.r².10 = 120 phi
1/3.r².10 = 120
10/3 . r² = 120
r² = 120 : 10/3
r² = 120 . 3/10
r² = 12.3
r² = 36
r = √36
r = 6 cm


3)
a.
Lp kerucut = 225 phi
phi.r.(r+s) = 225 phi
phi.r.(r+16) = 225 phi
r²+16r = 225
r²+16r-225 = 0
(r-9).(r+25) = 0
r-9 = 0
r = 9
atau
r+25 = 0
r = -25 (tdk memenuhi)

jadi,
t = √(s²-r²)
= √(16²-9²)
= √(256-81)
= √175
= √(25.7)
= 5√7 cm


b)
d = 15 cm → r = 7,5 cm
maka,
V kerucut = 150 phi
1/3.phi.r².t = 150 phi
1/3.phi.(7,5)².t = 150 phi
1/3.phi.56,25.t = 150 phi
1/3 . 56,25 . t = 150
56,25/3 . t = 150
t = 150 : 56,25/3
t = 150 . 3/56,25
t = 8 cm