The figure shows a container made up of 3 sections. Cuboid S with a square base of side 14 cm and height 40 cm. Cube T with a side of 16 cm. Cuboid U that is 64 cm by 24 cm by 43 cm. Water from a tap above flows down at a rate of 2.8 litres per minute while water is drained out from the bottom at a rate of 1 litre per minute. How long did it take to fill up the container to a height of 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of T
= 16 x 16 x 16
= 4096 cm³ 

Volume of U
= 64 x 24 x 43
= 66048 cm³ 

1 ℓ = 1000 cm³ 
2.8 ℓ = 2800 cm³ 

Net increase in volume per minute
= 2800 - 1000
= 1800 cm³/min

Height of S to be filled with water
= 69 - (43 + 16)
= 10 cm

Volume of water in S
= 14 x 14 x 10
= 1960 cm³ 

Volume of water in U, T and part of S
= 66048 + 4096 + 1960
= 72104 cm³ 

Time taken to reach height
= 72104 ÷ 1800
≈ 40 min (Correct to nearest whole number)

Answer(s): 40 min