A rectangular tank 120 cm by 60 cm by 44 cm was 30% filled with water. A tap was turned on to fill it up with water at a rate of 5 ℓ/min. Every 30 seconds after the tap was turned on, an iron ball of volume 500 cm3 was added to the tank. How many iron balls of the same volume would there be in the tank when the tank is 100% filled with water?
Percentage of volume of space to be filled
= 100% - 30%
= 70%
Volume of space in the tank
= 70% x 120 x 60 x 44
=
70100 x 120 x 60 x 44
= 221760 cm
3 1 ℓ = 1000 mℓ
5 ℓ = 5 x 1000 = 5000 mℓ
Number of sets of 30 seconds in 1 min
= 60 ÷ 30
= 2
Water flowed in every 30 seconds
= 5000 ÷ 2
= 2500 mℓ
Total volume added for every 30 seconds
= 2500 + 500
= 3000 cm
3 Number of sets of 3000 cm
3= 221760 ÷ 3000
= 73 r 2760
After the last iron ball is added, 2760 cm
3 of water will flow into the tank so that the tank is 100% filled with water.
Number of iron balls added = 73
Answer(s): 73
