harga 5kg gula dan 3kg tepung Rp 50.400. sedangkan harga 3kg gula dan 5kg tepung Rp38.400. jika ibu membeli 1 kg gula dan 2kg tepung, maka uang yg garus divayar

misal,
harga 1 kg gula = x
harga 1 kg tepung = y

maka,
5x + 3y = Rp.50.400 | ×5 |
3x + 5y = Rp.38.400 | ×3 |

25x + 15y = Rp.252.000
9x + 15y = Rp.115.200
------------------------------------ -
16x = Rp.136.800
x = Rp.8.550

substitusikan x = Rp.8.550 ke persamaan 3x + 5y = Rp.38.400
3x + 5y = Rp.38.400
3 × Rp.8.550 + 5y = Rp.38.400
Rp.25.650 + 5y = Rp.38.400
Rp.38.400 - Rp.25.650 = 5y
Rp.12.750 = 5y
y = Rp.2.550

x + 2y
= 1 × Rp.8.550 + 2 × Rp.2.550
= Rp.8.550 + Rp.5.100
= Rp.13.650

jadi, harga 1 kg gula dan 2 kg tepung adalah Rp.13.650

Misal :
harga gula = x
harga tepung = y

Maka :
5x + 3y = 50.400 (× 5)
3x + 5y = 38.400 (× 3)

25x + 15y = 252.000
...9x + 15y = 115.200
-------------------------------- -
16x = 136.800
x = 136.800/16
x = 8.550

5x + 3y = 50.400
5(8.550) + 3y = 50.400
42.750 + 3y = 50.400
3y = 50.400 - 42.750
3y = 7.650
y = 7.650/3
y = 2.550


x + 2y
= 8.550 + 2(2.550)
= 8.550 + 5.100
= 13.650

Jadi uang yang harus dibayarkan adalah Rp 13.650,00