Two identical pails T and U contained some water. Pail T was ¹₄ filled and Pail U was ¹₅ filled. The ratio of the total mass of Pail T and the water in it to the total mass of Pail U and the water in it was 8 : 7. The total mass of the two pails and the water they contained was 3450 g. What is the mass of an empty pail?
Mass of Pail T and the water inside = 8 u
Mass of Pail U 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 = 3450

1 u = 3450 ÷ 15 = 230

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

Fraction of the water that Pail T had more than Pail U 
= 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 230
= 690 g

Answer(s): 690 g