Two identical pails Y and Z contained some water. Pail Y was ¹₅ filled and Pail Z was ¹₆ filled. The ratio of the total mass of Pail Y and the water in it to the total mass of Pail Z and the water in it was 9 : 8. The total mass of the two pails and the water they contained was 2550 g. What is the mass of an empty pail?
Mass of Pail Y and the water inside = 9 u
Mass of Pail Z and the water inside = 8 u

Total mass of the two pails and the water inside them
= 9 u + 8 u
= 17 u

17 u = 2550

1 u = 2550 ÷ 17 = 150

Mass of Pail Y and the water in it more than mass of Pail Z and the water in it 
= 9 u - 8 u
= 1 u

Fraction of the water that Pail Y had more than Pail Z 
= ¹₅ - ¹₆
= ⁶₃₀ - ⁵₃₀
= ¹₃₀ 

¹₃₀ of the water capacity → 1 u
⁵₃₀ of the water capacity → 5 x 1 u = 5 u

Mass of an empty pail
= 8 u - 5 u
= 3 u
= 3 x 150
= 450 g

Answer(s): 450 g