A container filled with 10 honeydews has a mass of 6.81 kg. The same container when filled with 4 oranges has a mass of 0.65 kg. The mass of 1 honeydew is six times the mass of 1 orange. Find the mass of the container when it is empty. Express the answer in g.
1 kg = 1000 g

6.81 kg = 6810 g
0.65 kg = 650 g

1 orange = 1 u
4 oranges = 4 x 1 u = 4 u

1 container + 4 oranges = 650
1 container + 4 u = 650 --- (1)

1 honeydew = 6 u
10 honeydews = 10 x 6 u = 60 u

1 container + 10 honeydews = 6810
1 container + 60 u = 6810 --- (2)

(2) - (1)
60 u - 4 u = 6810 - 650
56 u = 6160

1 u = 6160 ÷ 56 = 110

4 u = 4 x 110 = 440

From (1):
1 container + 4 u = 650
1 container + 440 = 650
 
1 container = 650 - 440 = 210

Mass of 1 container = 210 g

Answer(s): 210 g