Question

Sebuah kotak panjangnya 1 1/2 kali lebar dan 4 1/2 kali tingginya. jumlah semua rusuk 408 cm. tentukan volume dan luas permukaannya

Answer 1

P = 3/2 l = 9/2 t
p = 3/2 l = l = p × 2/3
p = 9/2 t = t = p × 2/9
panjang kerangka = 4 (p + l + t)
408 = 4 (p + 2p/3 + 2p/9)
102 = p/1 + 2p/3 + 2p/9
102 = 9p/9 + 6p/9 + 2p/9
918 = 17p
p = 918/17 = 54 cm
l = p × 2/3 = 54 × 2/3 = 36 cm
t = p × 2/9 = 54 × 2/9 = 12 cm
luas permukaan =
2( pl + pt + lt)
2 (54 × 36 + 54 × 12 + 36 × 12)
2 (1944 + 648 + 432)
2(3024) = 6048 cm2

volume = p × l × t
= 54 × 36 × 12
= 1944 ×12
= 23328 cm3