A box filled with 10 jackfruits has a mass of 7.72 kg. The same box when filled with 9 mangoes has a mass of 1.57 kg. The mass of 1 jackfruit is five times the mass of 1 mango. Find the mass of the box when it is empty. Express the answer in g.
1 kg = 1000 g

7.72 kg = 7720 g
1.57 kg = 1570 g

1 mango = 1 u
9 mangoes = 9 x 1 u = 9 u

1 box + 9 mangoes = 1570
1 box + 9 u = 1570 --- (1)

1 jackfruit = 5 u
10 jackfruits = 10 x 5 u = 50 u

1 box + 10 jackfruits = 7720
1 box + 50 u = 7720 --- (2)

(2) - (1)
50 u - 9 u = 7720 - 1570
41 u = 6150

1 u = 6150 ÷ 41 = 150

9 u = 9 x 150 = 1350

From (1):
1 box + 9 u = 1570
1 box + 1350 = 1570
 
1 box = 1570 - 1350 = 220

Mass of 1 box = 220 g

Answer(s): 220 g