tolong Bantu jawab nomor 18 Dan nomor 3

#18
Alas : tinggi = 5 : 4
Alas asli = 5n
Tinggi asli = 4n
Luas = 160 cm²

L = 1/2 x a x t
160 = 1/2 x 5n x 4n
160 = 5n x 2n
160 = 10n²
n = √(160/10)
n = √16
n = 4
Tinggi asli = 4n = 4 x 4 = 16 cm
Alas asli = 5n = 5 x 4 = 20 cm

KOREKSI
1/2 x 16 x 20 = 160 cm²

#3
L total = (1/2 x 13 x 14 + 1/2 x 9 x 18) - 1/2 x 9 x 6
= 91 + 81 - 27
= 172 - 27
= 145 cm²

Luas yang diarsir = 145 - (1/2 x 9 x 6) - (1/2 x 14 x 4)
= 145 - 27 - 28
= 90 cm²