Jika keliling persegi panjang tersebut 120 cm.ukuran panjangnya adalah.... Cm

l = 20 cm
K = 120cm
2(p+l) = 120cm
p+l = 120/2
p+20 = 60
p = 60-20
p = 40cm

Kpp = 2p + 2l
120 = 2p + 2.25
120 = 2p + 50
120-50 = 2p
70 = 2p
p = 70/2
p = 35

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