Jawaban:
Luas persegi panjang = p × l
Keliling persegi panjang = 2(p + l)
Pembahasan
a. Panjang = 14 cm
Keliling = 48 cm
Lebar = .... ? Luas = ... ?
Jawab
Keliling = 48 cm
2(p + l) = 48 cm
(p + l) = \frac{48 \: cm}{2}
14 cm + l = 24 cm
l = 24 cm – 14 cm
l = 10 cm
Lebar = 10 cm
Luas = p × l
Luas = 14 cm × 10 cm
Luas = 140 cm²
b. Panjang 20 cm
Luas = 640 cm²
Lebar = ... ? Keliling = ... ?
Jawab
Luas = 640 cm²
p × l = 640 cm²
20 cm × l = 640 cm²
l = \frac{640 \: cm^{2}}{20 \: cm}
l = 32 cm
Lebar = 32 cm
Keliling = 2(p + l)
Keliling = 2(20 cm + 32 cm)
Keliling = 2(52 cm)
Keliling = 104 cm
c. Lebar = 12 cm
Keliling = 84 cm
Panjang = ... ? Luas = ... ?
Jawab
Keliling = 84 cm
2(p + l) = 84 cm
(p + l) = \frac{84 \: cm}{2}
p + 12 cm = 42 cm
p = 42 cm – 12 cm
p = 30 cm
Panjang = 30 cm
Luas = p × l
Luas = 30 cm × 12 cm
Luas = 360 cm²
d. Lebar = 30 cm
Keliling = 130 cm
Panjang = .... ? Luas = .... ?
Jawab
Keliling = 130 cm
2(p + l) = 130 cm
(p + l) = \frac{130 \: cm}{2}
p + 30 cm = 65 cm
p = 65 cm – 30 cm
p = 35 cm
Panjang = 35 cm
Luas = p × l
Luas = 35 cm × 30 cm
Luas = 1.050 cm²
