Kunci Jawaban Matematika Kelas 9 Halaman 280 Latihan 5.1, Menghitung Volume dan Luas Permukaan Tabung

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. Misalkan tabung tersebut memiliki volume V cm³ dan luas permukaan L cm². Apakah mungkin V = L?
Jika ya, tentukan nilai 1/r + 1/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

Jadi, nilai 1/r + 1/t = 1/2.