luas alas kerucut 154 cm2.jika panjang garis pelukisnya 20cm, maka luas selimut kerucut tersebut adalah.............. pake caranya yaa

Kelas 9 Matematika
Bab 2 - Bangun Ruang Sisi Lengkung

Kerucut
La = 154 cm²
s = 20 cm

La = πr²
r² = La/π
r² = 154/ 22/7
r² = 154 × 7/22
r² = 49
r = √49
r = 7 cm

Luas selimut
Ls = πrs
Ls = 22/7 × 7 cm × 20 cm
Ls = 22 cm × 20 cm
Ls = 440 cm²

La = phi.r2
154cm2 = 22/7 . R2
154.7/22 = r2
49 = r2
R = 7
S = 20
Lsel = phi.r.s
= 22/7 . 7 . 20
= 440cm2