A rectangular container 80 cm by 40 cm by 50 cm was 30% filled with water. A tap was turned on to fill it up with water at a rate of 9 ℓ/min. Every 15 seconds after the tap was turned on, an iron ball of volume 500 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% - 30%
= 70%
Volume of space in the container
= 70% x 80 x 40 x 50
=
70100 x 80 x 40 x 50
= 112000 cm
3 1 ℓ = 1000 mℓ
9 ℓ = 9 x 1000 = 9000 mℓ
Number of sets of 15 seconds in 1 min
= 60 ÷ 15
= 4
Water flowed in every 15 seconds
= 9000 ÷ 4
= 2250 mℓ
Total volume added for every 15 seconds
= 2250 + 500
= 2750 cm
3 Number of sets of 2750 cm
3= 112000 ÷ 2750
= 40 r 2000
After the last iron ball is added, 2000 cm
3 of water will flow into the tank so that the container is 100% filled with water.
Number of iron balls added = 40
Answer(s): 40
