A box filled with 14 mangoes has a mass of 10.94 kg. The same box when filled with 8 oranges has a mass of 1.82 kg. The mass of 1 mango is four times the mass of 1 orange. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

10.94 kg = 10940 g
1.82 kg = 1820 g

1 orange = 1 u
8 oranges = 8 x 1 u = 8 u

1 box + 8 oranges = 1820
1 box + 8 u = 1820 --- (1)

1 mango = 4 u
14 mangoes = 14 x 4 u = 56 u

1 box + 14 mangoes = 10940
1 box + 56 u = 10940 --- (2)

(2) - (1)
56 u - 8 u = 10940 - 1820
48 u = 9120

1 u = 9120 ÷ 48 = 190

8 u = 8 x 190 = 1520

From (1):
1 box + 8 u = 1820
1 box + 1520 = 1820
 
1 box = 1820 - 1520 = 300

Mass of 1 box = 300 g

Answer(s): 300 g