The figure is not drawn to scale. Tank W measuring 50 cm by 42 cm by 20 cm contained 21.5 ℓ of water. Tank X measuring 40 cm by 25 cm by 34 cm contained 20 ℓ of water. Jeremy poured some water from Tank W into Tank X without spilling and the water level of Tank X rose to 31 cm. What was the height of water level left in Tank W?
1 ℓ = 1000 cm³
20 ℓ = 20000 cm³
21.5 ℓ = 21.5 x 1000 = 21500 cm³

Height of water in Tank X at first
= 20000 ÷ 40 ÷ 25
= 20 cm

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

Volume of water poured into Tank X
= 40 x 25 x 11
= 11000 cm³ 

Volume of water left in Tank W
= 21500 - 11000
= 10500 cm³ 

Height of water left in Tank W
= 10500 ÷ 50 ÷ 42
= 5 cm

Answer(s): 5 cm