The figure shows a tank made up of 3 sections. Cuboid J with a square base of side 14 cm and height 37 cm. Cube K with a side of 10 cm. Cuboid L that is 73 cm by 11 cm by 40 cm. Water from a tap above flows down at a rate of 3.6 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 58 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of K
= 10 x 10 x 10
= 1000 cm³ 

Volume of L
= 73 x 11 x 40
= 32120 cm³ 

1 ℓ = 1000 cm³ 
3.6 ℓ = 3600 cm³ 

Net increase in volume per minute
= 3600 - 1000
= 2600 cm³/min

Height of J to be filled with water
= 58 - (40 + 10)
= 8 cm

Volume of water in J
= 14 x 14 x 8
= 1568 cm³ 

Volume of water in L, K and part of J
= 32120 + 1000 + 1568
= 34688 cm³ 

Time taken to reach height
= 34688 ÷ 2600
≈ 13 min (Correct to nearest whole number)

Answer(s): 13 min