The figure is not drawn to scale. Tank Y measuring 50 cm by 47 cm by 25 cm contained 20.15 ℓ of water. Tank Z measuring 40 cm by 35 cm by 32 cm contained 35 ℓ of water. Gabriel poured some water from Tank Y into Tank Z without spilling and the water level of Tank Z rose to 31 cm. What was the height of water level left in Tank Y?
1 ℓ = 1000 cm³
35 ℓ = 35000 cm³
20.15 ℓ = 20.15 x 1000 = 20150 cm³

Height of water in Tank Z at first
= 35000 ÷ 40 ÷ 35
= 25 cm

Increase in the height of water in Tank Z
= 31 - 25
= 6 cm

Volume of water poured into Tank Z
= 40 x 35 x 6
= 8400 cm³ 

Volume of water left in Tank Y
= 20150 - 8400
= 11750 cm³ 

Height of water left in Tank Y
= 11750 ÷ 50 ÷ 47
= 5 cm

Answer(s): 5 cm