A rectangular tank 90 cm by 60 cm by 47 cm was 20% filled with water. A tap was turned on to fill it up with water at a rate of 5 ℓ/min. Every 15 seconds after the tap was turned on, an iron ball of volume 500 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 60 x 47
=
80100 x 90 x 60 x 47
= 203040 cm
3 1 ℓ = 1000 mℓ
5 ℓ = 5 x 1000 = 5000 mℓ
Number of sets of 15 seconds in 1 min
= 60 ÷ 15
= 4
Water flowed in every 15 seconds
= 5000 ÷ 4
= 1250 mℓ
Total volume added for every 15 seconds
= 1250 + 500
= 1750 cm
3 Number of sets of 1750 cm
3= 203040 ÷ 1750
= 116 r 40
After the last iron ball is added, 40 cm
3 of water will flow into the tank so that the tank is 100% filled with water.
Number of iron balls added = 116
Answer(s): 116