Two identical pails W and X contained some water. Pail W was ¹₄ filled and Pail X was ¹₅ filled. The ratio of the total mass of Pail W and the water in it to the total mass of Pail X and the water in it was 8 : 7. The total mass of the two pails and the water they contained was 2250 g. What is the mass of an empty pail?
Mass of Pail W and the water inside = 8 u
Mass of Pail X and the water inside = 7 u

Total mass of the two pails and the water inside them
= 8 u + 7 u
= 15 u

15 u = 2250

1 u = 2250 ÷ 15 = 150

Mass of Pail W and the water in it more than mass of Pail X and the water in it 
= 8 u - 7 u
= 1 u

Fraction of the water that Pail W had more than Pail X 
= ¹₄ - ¹₅
= ⁵₂₀ - ⁴₂₀
= ¹₂₀ 

¹₂₀ of the water capacity → 1 u
⁴₂₀ of the water capacity → 4 x 1 u = 4 u

Mass of an empty pail
= 7 u - 4 u
= 3 u
= 3 x 150
= 450 g

Answer(s): 450 g