A rectangular tank 110 cm by 50 cm by 42 cm was 10% filled with water. A tap was turned on to fill it up with water at a rate of 8 ℓ/min. Every 30 seconds after the tap was turned on, an iron ball of volume 200 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% - 10%
= 90%
Volume of space in the tank
= 90% x 110 x 50 x 42
=
90100 x 110 x 50 x 42
= 207900 cm
3 1 ℓ = 1000 mℓ
8 ℓ = 8 x 1000 = 8000 mℓ
Number of sets of 30 seconds in 1 min
= 60 ÷ 30
= 2
Water flowed in every 30 seconds
= 8000 ÷ 2
= 4000 mℓ
Total volume added for every 30 seconds
= 4000 + 200
= 4200 cm
3 Number of sets of 4200 cm
3= 207900 ÷ 4200
= 49 r 2100
After the last iron ball is added, 2100 cm
3 of water will flow into the tank so that the tank is 100% filled with water.
Number of iron balls added = 49
Answer(s): 49
