Two identical tanks H and J contained some water. Tank H was ¹₄ filled and Tank J was ¹₅ filled. The ratio of the total mass of Tank H and the water in it to the total mass of Tank J and the water in it was 9 : 8. The total mass of the two tanks and the water they contained was 4250 g. What is the mass of an empty tank?
Mass of Tank H and the water inside = 9 u
Mass of Tank J and the water inside = 8 u

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

17 u = 4250

1 u = 4250 ÷ 17 = 250

Mass of Tank H and the water in it more than mass of Tank J and the water in it 
= 9 u - 8 u
= 1 u

Fraction of the water that Tank H had more than Tank J 
= 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 tank
= 8 u - 4 u
= 4 u
= 4 x 250
= 1000 g

Answer(s): 1000 g