A container filled with 8 durians has a mass of 3.68 kg. The same container when filled with 3 mangoes has a mass of 0.49 kg. The mass of 1 durian is four times the mass of 1 mango. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

3.68 kg = 3680 g
0.49 kg = 490 g

1 mango = 1 u
3 mangoes = 3 x 1 u = 3 u

1 container + 3 mangoes = 490
1 container + 3 u = 490 --- (1)

1 durian = 4 u
8 durians = 8 x 4 u = 32 u

1 container + 8 durians = 3680
1 container + 32 u = 3680 --- (2)

(2) - (1)
32 u - 3 u = 3680 - 490
29 u = 3190

1 u = 3190 ÷ 29 = 110

3 u = 3 x 110 = 330

From (1):
1 container + 3 u = 490
1 container + 330 = 490
 
1 container = 490 - 330 = 160

Mass of 1 container = 160 g

Answer(s): 160 g