A rectangular tank 90 cm by 50 cm by 48 cm was 20% filled with water. A tap was turned on to fill it up with water at a rate of 9 ℓ/min. Every 10 seconds after the tap was turned on, an iron ball of volume 100 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% - 20%
= 80%
Volume of space in the tank
= 80% x 90 x 50 x 48
=
80100 x 90 x 50 x 48
= 172800 cm
3 1 ℓ = 1000 mℓ
9 ℓ = 9 x 1000 = 9000 mℓ
Number of sets of 10 seconds in 1 min
= 60 ÷ 10
= 6
Water flowed in every 10 seconds
= 9000 ÷ 6
= 1500 mℓ
Total volume added for every 10 seconds
= 1500 + 100
= 1600 cm
3 Number of sets of 1600 cm
3= 172800 ÷ 1600
= 108 r 0
After the last iron ball is added, 0 cm
3 of water will flow into the tank so that the tank is 100% filled with water.
Number of iron balls added = 108
Answer(s): 108