harga pembelian =10.000,00 harga penjualan = untung= persentase untung=20%

p. untung = (keuntungan/pembelian) x 100%
20% = ( k / 10 000 ) x 100%
20%/100% = k/ 10 000
1/5 = k / 10 000
k = 10 000/5
k = 2000

jadi penjualan :
= pembelian + untung
= 10 000 + 2 000
= 12 000