The figure is not drawn to scale. Tank Z measuring 50 cm by 45 cm by 20 cm contained 33.4 ℓ of water. Tank A measuring 40 cm by 35 cm by 36 cm contained 28 ℓ of water. Luke poured some water from Tank Z into Tank A without spilling and the water level of Tank A rose to 31 cm. What was the height of water level left in Tank Z?
1 ℓ = 1000 cm³
28 ℓ = 28000 cm³
33.4 ℓ = 33.4 x 1000 = 33400 cm³

Height of water in Tank A at first
= 28000 ÷ 40 ÷ 35
= 20 cm

Increase in the height of water in Tank A
= 31 - 20
= 11 cm

Volume of water poured into Tank A
= 40 x 35 x 11
= 15400 cm³ 

Volume of water left in Tank Z
= 33400 - 15400
= 18000 cm³ 

Height of water left in Tank Z
= 18000 ÷ 50 ÷ 45
= 8 cm

Answer(s): 8 cm