Kunci Jawaban Matematika Kelas 9: Tentukan Panjang dari Unsur Tabung yang Ditanyakan

c) Luas = (2π x 4 x 4) + (2π x 4 x 12)
= 32π + 96π 
= 128π cm⊃2;
Volume = π x 4 x 4 x 12
= 192π cm⊃3;

d) Luas = (2π x 1 x 1) + (2π x 1 x 8)
= 2π + 16π 
= 18π m⊃2;
Volume = π x 1 x 1 x 8
= 8π m⊃3;

e) Luas = (2π x 2 x 2) + (2π x 2 x 10)
= 8π + 40π 
= 48π m⊃2;
Volume = π x 2 x 2 x 10
= 40π m⊃3;

f ) Luas = (2π x 3,5 x 3,5) + (2π x 3,5 x 20)
= 24,5π + 140π 
= 164,5π cm⊃2;
Volume = π x 3,5 x 3,5 x 20
= 245π cm⊃3;

2. Tentukan panjang dari unsur tabung yang ditanyakan.

Jawaban :

a) V = π x r x r x t
600π = π x 10 x 10 x t
t = 600π / 100π
t = 6 cm

b) L = 2π x r x (r + t)
120π = 2π x 5 x (5 + t)
5 + t = 120π / 10π
5 + t = 12
t = 7 cm

c) V = π x r x r x t
224π = π x 4 x 4 x t
t = 224π / 16π
t = 14 cm

d) L = 2π x r x (r + t)
528π = 2π x r x (r + 13)
528π = 2π x r⊃2; + 13r
r⊃2; + 13r - 264 = 0
(r + 24) (r - 11)
r = 11 cm

e) L = 2π x r x (r + t)
450π = 2π x r x (r + 15)
450π = 2π x r⊃2; + 15r
r⊃2; + 15r - 225 = 0
r = 9 cm

f) V = π x r x r x t
294π = π x r x r x 6 
r⊃2; = 294π / 6π
r = √49
r = 7 cm

3. Berpikir Kritis. Terdapat suatu tabung dengan jari-jari r cm dan tinggi tabung t cm, dimana r < t>

Jawaban :

V = L
2πr(r + t) = πr⊃2;t
2(r + t) = rt
(r + t) / rt = 1/2
1/r + 1/t = 1/2