Tolong bantuannya.. Saya mau latihan dirumah.. Kalau bisa jawabannya jelas ya..

31.
panjang kawat = s × 12 + t × 6
panjang kawat = (12 × 12) cm + (30 × 6) cm
= 144 cm + 180 cm
= 324 cm

39.
rata2 = [(x1 × n1) + (x2 + n2)] / (n1 + n2)
rata2 = [(60 × 4) + (70 × 1)] / (4 + 1)
rata2 = [240 + 70] / 5
rata2 = 310/5
rata2 = 62

Rata-rata nilai matematika 4 orang siswa = 60
nilai seorang siswa ulangan susulan = 70
...........................................(4 × 60) + 70
rata-rata lima siswa = -----------------------
...................................................4 +1
.....240 + 70
= -----------------
............5
.........310
= --------------
..........5
= 62

Jadi nilai rata-rata lima siswa tersebut adalah
62 (C)

Kerangka prisma segienam beraturan
s = 12 cm
t = 30 cm

panjang kawat minimum = (2 × 6 × s) + (6 × t)
= (2 × 6 × 12) + (6 × 30)
= 144 + 180
= 324
jadi panjang kawat minimum adalah
324 cm (B)