Suatu kelas terdiri dari 12 siswa laki-laki dan 18 siswa perempuan. Jika rata-rata berat badan siswa perempuan adalah 40 kg dan rata-rata berat badan siswa laki-laki adalah 38 kg, berapakah rata-rata berat seluruh siswa di kelas itu?

<p>Rata-rata berat badan siswa = Jumlah berat badan siswa : Jumlah siswa</p><p>Jumlah berat badan siswa = Rata-rata berat badan siswa x Jumlah siswa</p><p>&nbsp;</p><p>Misalkan:</p><p>Siswa perempuan = p</p><p>Siswa laki-laki = l</p><p>&nbsp;</p><p>Diketahui:&nbsp;</p><p>Jumlah siswa l = 12 siswa</p><p>Jumlah siswa p = 18 siswa</p><p>Rata - rata berat badan siswa l = 38 kg</p><p>Rata - rata berat badan siswa p = 40 kg</p><p>&nbsp;</p><p>Penyelesaian</p><p>Jumlah berat badan siswa p = 40 kg x 18</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 720 kg</p><p>Jumlah berat badan siswa p = 38 kg x 12</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= &nbsp;456 kg</p><p>Rata-rata berat seluruh siswa = (720 kg + 456 kg) : (12 + 18)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 1.176 kg : 30</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= <strong>39,2 kg</strong></p>