A rectangular container 90 cm by 60 cm by 43 cm was 20% filled with water. A tap was turned on to fill it up with water at a rate of 8 ℓ/min. Every 15 seconds after the tap was turned on, an iron ball of volume 600 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% - 20%
= 80%
Volume of space in the container
= 80% x 90 x 60 x 43
=
80100 x 90 x 60 x 43
= 185760 cm
3 1 ℓ = 1000 mℓ
8 ℓ = 8 x 1000 = 8000 mℓ
Number of sets of 15 seconds in 1 min
= 60 ÷ 15
= 4
Water flowed in every 15 seconds
= 8000 ÷ 4
= 2000 mℓ
Total volume added for every 15 seconds
= 2000 + 600
= 2600 cm
3 Number of sets of 2600 cm
3= 185760 ÷ 2600
= 71 r 1160
After the last iron ball is added, 1160 cm
3 of water will flow into the tank so that the container is 100% filled with water.
Number of iron balls added = 71
Answer(s): 71
