A container filled with 10 king melons has a mass of 5.44 kg. The same container when filled with 7 mangosteens has a mass of 1.15 kg. The mass of 1 king melon is four times the mass of 1 mangosteen. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

5.44 kg = 5440 g
1.15 kg = 1150 g

1 mangosteen = 1 u
7 mangosteens = 7 x 1 u = 7 u

1 container + 7 mangosteens = 1150
1 container + 7 u = 1150 --- (1)

1 king melon = 4 u
10 king melons = 10 x 4 u = 40 u

1 container + 10 king melons = 5440
1 container + 40 u = 5440 --- (2)

(2) - (1)
40 u - 7 u = 5440 - 1150
33 u = 4290

1 u = 4290 ÷ 33 = 130

7 u = 7 x 130 = 910

From (1):
1 container + 7 u = 1150
1 container + 910 = 1150
 
1 container = 1150 - 910 = 240

Mass of 1 container = 240 g

Answer(s): 240 g