Kunci Jawaban Matematika Kelas 9 Halaman 280 281 282 283 Luas Permukaan dan Volume Bangun Tabung

Luas permukaan tabung = (2π x r x r) + (2π x r x t) = 2 x r x (r + t)
Volume tabung = π x r x r x t

a) Luas = (2π x 4 x 4) + (2π x 4 x 10)
= 32π + 80π
= 112π cm2;
Volume = π x 4 x 4 x 10
= 160π cm3;

b) Luas = (2π x 7 x 7) + (2π x 7 x 6)
= 98π + 84π
= 182π cm2;
Volume = π x 7 x 7 x 6
= 294π cm3;

c) Luas = (2π x 4 x 4) + (2π x 4 x 12)
= 32π + 96π
= 128π cm2;
Volume = π x 4 x 4 x 12
= 192π cm3;

d) Luas = (2π x 1 x 1) + (2π x 1 x 8)
= 2π + 16π
= 18π m2;
Volume = π x 1 x 1 x 8
= 8π m3;

e) Luas = (2π x 2 x 2) + (2π x 2 x 10)
= 8π + 40π
= 48π m2;
Volume = π x 2 x 2 x 10
= 40π m3;

f ) Luas = (2π x 3,5 x 3,5) + (2π x 3,5 x 20)
= 24,5π + 140π
= 164,5π cm2;
Volume = π x 3,5 x 3,5 x 20
= 245π cm3;

Baca juga: Kunci Jawaban Seni Budaya Kelas 9 Halaman 197, Sebutkan Perbedaan Gaya Bernyanyi Berbagai Jenis Lagu

2. Tentukan panjang dari unsur tabung yang ditanyakan

Ket: V = volume tabung, L = luas permukaan tabung, r = jari-jari tabung, t = tinggi tabung.

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