A box filled with 11 jackfruits has a mass of 10.72 kg. The same box when filled with 10 persimmons has a mass of 2.17 kg. The mass of 1 jackfruit is five times the mass of 1 persimmon. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

10.72 kg = 10720 g
2.17 kg = 2170 g

1 persimmon = 1 u
10 persimmons = 10 x 1 u = 10 u

1 box + 10 persimmons = 2170
1 box + 10 u = 2170 --- (1)

1 jackfruit = 5 u
11 jackfruits = 11 x 5 u = 55 u

1 box + 11 jackfruits = 10720
1 box + 55 u = 10720 --- (2)

(2) - (1)
55 u - 10 u = 10720 - 2170
45 u = 8550

1 u = 8550 ÷ 45 = 190

10 u = 10 x 190 = 1900

From (1):
1 box + 10 u = 2170
1 box + 1900 = 2170
 
1 box = 2170 - 1900 = 270

Mass of 1 box = 270 g

Answer(s): 270 g