Keliling persegi panjand ABCD = 106cm jika AD = 21cm maka AB = ?

106-(21+21)
= 106 - 42
=64

64÷2= 32

pembuktian
32+32+21+21=
64+42=106

Keliling = 106
Anggap lebar = 21

Keliling = 2 (p+l)
106 = 2 (p+21)
106 = 2p + 42
2p = 106 - 42
2p = 64
p = 32