dalam ruang pertunjukan terdapat 25 kursi pada baris pertama 27 pada baris kedua dan setiap baris berikut memuat dua kursi lebih banyak dari baris di depan jika di dalam ruang tersebut dipasang 12 baris tentukan ditambah berapa baris lagi untuk undang-undang 500 orang

<p>25, 27, 29, ....</p><p>a = 25</p><p>b = 27 - 25 = 2</p><p>n = 12</p><p>&nbsp;</p><ul><li>Mencari jumlah kursi (S₁₂)</li></ul><p>&nbsp; &nbsp; &nbsp; S_n = n/2 (2a + (n - 1)b)</p><p>&nbsp; &nbsp; &nbsp; S₁₂ = 12/2 (2(25) + (12 - 1)2)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 6 (50 + (11)2)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 6 (50 + 22)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 6 (72)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; = 432 kursi</p><p>&nbsp; &nbsp; &nbsp;Jumlah 12 baris kursi adalah 432 kursi</p><p>&nbsp;</p><ul><li>Menentukan tambahan kursi&nbsp;</li></ul><p>&nbsp; &nbsp; &nbsp; Tambahan kursi = Jumlah tamu Undangan - Jumlah Kursi</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 500 - 432</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 68 kursi</p><p>&nbsp; &nbsp; &nbsp; Tambahan kursi sebanyak 68 kursi atau tambah 2 baris lagi</p>