20. Diketahui prisma tegak segitiga siku-siku dengan volume 1.632 cm persegi, jika keliling alas prisma 48cm dan perbandingan sisi-sisi nya a : b : c= 5 : 3 : 4

Bab Bangun Ruang
Matematika SMP Kelas VIII

prisma tegak segitiga siku-siku
5p + 3p + 4p = 48
12p = 48
p = 48 : 12
p = 4

a = 5 x 4 = 20 cm
b = 3 x 4 = 12 cm
c = 4 x 4 = 16 cm

volume = 1/2 x b x c x tprisma = 1.632
1/2 x 12 x 16 x tprisma = 1.632
tprisma = 1.632 : 96
tprisma = 17 cm

A + b + c = keliling
5n + 3n + 4n = 48
12n = 48
n = 48 / 12
n = 4

a = 5n = 5(4) = 20 cm
b = 3n = 3(4) = 12 cm
c = 4n = 4(4) = 16 cm

Volume = luas alas × tinggi
Tinggi = 1632 / (12 × 16 × 1/2)
Tinggi = 1632 / 96
Tinggi = 17cm