The figure shows a tank made up of 3 sections. Cuboid R with a square base of side 14 cm and height 21 cm. Cube S with a side of 10 cm. Cuboid T that is 76 cm by 12 cm by 44 cm. Water from a tap above flows down at a rate of 2.7 litres per minute while water is drained out from the bottom at a rate of 2 litre per minute. How long did it take to fill up the tank to a height of 61 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of S
= 10 x 10 x 10
= 1000 cm³ 

Volume of T
= 76 x 12 x 44
= 40128 cm³ 

2 ℓ = 2000 cm³ 
2.7 ℓ = 2700 cm³ 

Net increase in volume per minute
= 2700 - 2000
= 700 cm³/min

Height of R to be filled with water
= 61 - (44 + 10)
= 7 cm

Volume of water in R
= 14 x 14 x 7
= 1372 cm³ 

Volume of water in T, S and part of R
= 40128 + 1000 + 1372
= 42500 cm³ 

Time taken to reach height
= 42500 ÷ 700
≈ 61 min (Correct to nearest whole number)

Answer(s): 61 min