A container filled with 11 mangoes has a mass of 10.25 kg. The same container when filled with 8 kiwis has a mass of 1.28 kg. The mass of 1 mango is seven 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

10.25 kg = 10250 g
1.28 kg = 1280 g

1 kiwi = 1 u
8 kiwis = 8 x 1 u = 8 u

1 container + 8 kiwis = 1280
1 container + 8 u = 1280 --- (1)

1 mango = 7 u
11 mangoes = 11 x 7 u = 77 u

1 container + 11 mangoes = 10250
1 container + 77 u = 10250 --- (2)

(2) - (1)
77 u - 8 u = 10250 - 1280
69 u = 8970

1 u = 8970 ÷ 69 = 130

8 u = 8 x 130 = 1040

From (1):
1 container + 8 u = 1280
1 container + 1040 = 1280
 
1 container = 1280 - 1040 = 240

Mass of 1 container = 240 g

Answer(s): 240 g