Matematika

Pertanyaan

keliling persegi panjang 80cm. jika selisih panjang dan lebarnya 12 cm, maka luasnya

2 Jawaban

  • K = 80
    p - l = 12
    p = 12 + l

    K = 80
    2(p + l) = 80
    p + l = 40
    12 + l + l = 40
    2l = 28
    l = 14 cm

    p = l + 12 = 14 + 12 = 26 cm

    L = p.l = 26 cm . 14 cm = 364 cm²
  • p - l = 12 cm
        p = l + 12 cm

    Keliling = 2 x ( p + l )
    80 cm   = 2 x ( l + 12 + l )
    80 cm   = 2 x (2l + 12)
    80 cm   = 4l + 24
             4l = 80 - 24
             4l = 56 cm
               l = 56 / 4
               l = 14 cm

    Lebar = 14 cm
    Panjang = 14 cm + 12 cm = 26 cm

    Luas persegi panjang
    = p x l
    = 26 cm x 14 cm
    = 364 cm²

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