The figure shows a tank made up of 3 sections. Cuboid T with a square base of side 14 cm and height 49 cm. Cube U with a side of 18 cm. Cuboid V that is 62 cm by 30 cm by 42 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 tank to a height of 70 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of U
= 18 x 18 x 18
= 5832 cm³ 

Volume of V
= 62 x 30 x 42
= 78120 cm³ 

1 ℓ = 1000 cm³ 
2.8 ℓ = 2800 cm³ 

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

Height of T to be filled with water
= 70 - (42 + 18)
= 10 cm

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

Volume of water in V, U and part of T
= 78120 + 5832 + 1960
= 85912 cm³ 

Time taken to reach height
= 85912 ÷ 1800
≈ 48 min (Correct to nearest whole number)

Answer(s): 48 min