9 identical 7-cm cubes are placed in an empty rectangular tank of length 81 cm and width 25 cm. The tank is then filled with water from a tap flowing at a rate of 9 litres per minute. It takes 8 minutes to fill up ³₄ of the tank. What is the height of the tank? Correct your answer to 1 decimal place.
Volume of 1 cube
= 7 x 7 x 7
= 343 cm³ 

Volume of 9 cubes
= 9 x 343
= 3087 cm³ 

1 ℓ = 1000 mℓ
9 ℓ = 9000 mℓ

Volume of water in the tank
= 8 x 9000
= 72000 mℓ

Volume of ³₄ of the tank
= 72000 + 3087
= 75087 mℓ

Volume of the tank
= 75087 ÷ ³₄
= 75087 x ⁴₃
= 100116 mℓ

Base area
= 81 x 25
= 2025 cm² 

Height of the tank
= 100116 ÷ 2025
≈ 49.4 cm

Answer(s): 49.4 cm