The figure is not drawn to scale. Tank B measuring 54 cm by 42 cm by 25 cm contained 27.64 ℓ of water. Tank C measuring 40 cm by 31 cm by 32 cm contained 31 ℓ of water. Ian poured some water from Tank B into Tank C without spilling and the water level of Tank C rose to 29 cm. What was the height of water level left in Tank B?
1 ℓ = 1000 cm³
31 ℓ = 31000 cm³
27.64 ℓ = 27.64 x 1000 = 27640 cm³

Height of water in Tank C at first
= 31000 ÷ 40 ÷ 31
= 25 cm

Increase in the height of water in Tank C
= 29 - 25
= 4 cm

Volume of water poured into Tank C
= 40 x 31 x 4
= 4960 cm³ 

Volume of water left in Tank B
= 27640 - 4960
= 22680 cm³ 

Height of water left in Tank B
= 22680 ÷ 54 ÷ 42
= 10 cm

Answer(s): 10 cm