Box L and Box M are identical. ⁴₅ of Box L and ⁵₈ of Box M are filled with sand. The mass of Box M with its contents is ⁹₁₀ the mass of Box L with its contents. The total mass of the two boxes with their contents is 532 kg. Find the mass of an empty box.
Mass of Box L and its contents = 10 u
Mass of Box M and its contents = 9 u

Total mass of the two boxes with their contents
= 10 u + 9 u
= 19 u

19 u = 532 

1 u = 532 ÷ 19 = 28

Mass of Box L with its concents more than mass of Box M with its contents
= 10 u - 9 u
= 1 u
= 1 x 28
= 28 kg

Fraction of the sand that Box L had more than Box M
= ⁴₅ - ⁵₈
= ³²₄₀ - ²⁵₄₀
= ⁷₄₀

⁷₄₀ of the capacity of sand in a box → 28
¹₄₀ of the capacity of sand in a box → 28 ÷ 7 = 4
²⁵₄₀ of the capacity of sand in a box → 25 x 4 = 100 

Mass of the sand and Box M
= 9 u
= 9 x 28
= 252 kg

Mass of the empty box
= 252 - 100
= 152 kg

Answer(s): 152 kg