A container filled with 9 durians has a mass of 8.15 kg. The same container when filled with 5 kiwis has a mass of 0.78 kg. The mass of 1 durian is eight times the mass of 1 kiwi. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

8.15 kg = 8150 g
0.78 kg = 780 g

1 kiwi = 1 u
5 kiwis = 5 x 1 u = 5 u

1 container + 5 kiwis = 780
1 container + 5 u = 780 --- (1)

1 durian = 8 u
9 durians = 9 x 8 u = 72 u

1 container + 9 durians = 8150
1 container + 72 u = 8150 --- (2)

(2) - (1)
72 u - 5 u = 8150 - 780
67 u = 7370

1 u = 7370 ÷ 67 = 110

5 u = 5 x 110 = 550

From (1):
1 container + 5 u = 780
1 container + 550 = 780
 
1 container = 780 - 550 = 230

Mass of 1 container = 230 g

Answer(s): 230 g