Box W and Box X are identical. ⁵₆ of Box W and ⁵₈ of Box X are filled with sand. The mass of Box X with its contents is ⁹₁₀ the mass of Box W with its contents. The total mass of the two boxes with their contents is 760 kg. Find the mass of an empty box.
Mass of Box W and its contents = 10 u
Mass of Box X and its contents = 9 u

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

19 u = 760 

1 u = 760 ÷ 19 = 40

Mass of Box W with its concents more than mass of Box X with its contents
= 10 u - 9 u
= 1 u
= 1 x 40
= 40 kg

Fraction of the sand that Box W had more than Box X
= ⁵₆ - ⁵₈
= ²⁰₂₄ - ¹⁵₂₄
= ⁵₂₄

⁵₂₄ of the capacity of sand in a box → 40
¹₂₄ of the capacity of sand in a box → 40 ÷ 5 = 8
¹⁵₂₄ of the capacity of sand in a box → 15 x 8 = 120 

Mass of the sand and Box X
= 9 u
= 9 x 40
= 360 kg

Mass of the empty box
= 360 - 120
= 240 kg

Answer(s): 240 kg