A rectangular container 120 cm by 60 cm by 49 cm was 10% 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 100 cm3 was added to the container. How many iron balls of the same volume would there be in the container when the container is 100% filled with water?
Percentage of volume of space to be filled
= 100% - 10%
= 90%
Volume of space in the container
= 90% x 120 x 60 x 49
=
90100 x 120 x 60 x 49
= 317520 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 + 100
= 2600 cm
3 Number of sets of 2600 cm
3= 317520 ÷ 2600
= 122 r 320
After the last iron ball is added, 320 cm
3 of water will flow into the tank so that the container is 100% filled with water.
Number of iron balls added = 122
Answer(s): 122
