The figure shows a container made up of 3 sections. Cuboid S with a square base of side 9 cm and height 44 cm. Cube T with a side of 10 cm. Cuboid U that is 73 cm by 19 cm by 50 cm. Water from a tap above flows down at a rate of 3.7 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 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of T
= 10 x 10 x 10
= 1000 cm³ 

Volume of U
= 73 x 19 x 50
= 69350 cm³ 

1 ℓ = 1000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 1000
= 2700 cm³/min

Height of S to be filled with water
= 70 - (50 + 10)
= 10 cm

Volume of water in S
= 9 x 9 x 10
= 810 cm³ 

Volume of water in U, T and part of S
= 69350 + 1000 + 810
= 71160 cm³ 

Time taken to reach height
= 71160 ÷ 2700
≈ 26 min (Correct to nearest whole number)

Answer(s): 26 min