18. Harga 4 buah buku dan 10 pensil rp45.000 jika harga 1 buku adalah 2 kali harga 1 pensil tentu harga masing-masing 1 pensil dan 1 buku adalah

<p>Misal:</p><p>Buku = b</p><p>Pensil = p</p><p>&nbsp;</p><p>Diketahui:</p><p>4b + 10p = Rp 45.000 &nbsp; &nbsp; &nbsp;(i)</p><p>1 b = 2 p &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;(ii)</p><p>Ditanya:</p><p>Harga 1 pensil dan 1 buku</p><p>&nbsp;</p><p>Karena:</p><p>1b = 2p</p><p>Subtitusikan ke persamaan (i)</p><p>&nbsp; 4b + 10 p = 45.000</p><p>4(2p)+10p = 45.000</p><p>&nbsp; &nbsp;8p + 10p = 45.000</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;18p = 45.000</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;p = 45.000 : 18</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;p = 2.500</p><p>Subtitusikan p=2.500 ke persamaan (ii):</p><p>1b = 2p</p><p>1b = 2(2.500)</p><p>1b = 5.000</p><p>&nbsp;</p><p>Jadi, harga 1 buku adalah Rp 5.000 dan 1 pensil adalah Rp 2.500.</p>