A rectangular tank 100 cm by 40 cm by 48 cm was 20% filled with water. A tap was turned on to fill it up with water at a rate of 10 ℓ/min. Every 15 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 100 x 40 x 48
=
80100 x 100 x 40 x 48
= 153600 cm
3 1 ℓ = 1000 mℓ
10 ℓ = 10 x 1000 = 10000 mℓ
Number of sets of 15 seconds in 1 min
= 60 ÷ 15
= 4
Water flowed in every 15 seconds
= 10000 ÷ 4
= 2500 mℓ
Total volume added for every 15 seconds
= 2500 + 100
= 2600 cm
3 Number of sets of 2600 cm
3= 153600 ÷ 2600
= 59 r 200
After the last iron ball is added, 200 cm
3 of water will flow into the tank so that the tank is 100% filled with water.
Number of iron balls added = 59
Answer(s): 59
