The figure shows 2 tanks, Tank F and Tank G. Tank G is completely empty while Tank F is filled with water to the brim. Water from Tap E flows in at a rate of 7.2 litres per minute while water drains from Tap D at a rate of 0.72 litres per minute. Both taps are turned on at the same time. After some time, the heights of the water level in both tanks became the same.
- Find the time taken for the heights of the water level to be the same in both tanks.
- Find the height of the water level at that point of time.
(a)
Base area of Tank F
= 40 x 20
= 800 cm
2 1 ℓ = 1000 cm
3 7.2 ℓ = 7200 cm
3 0.72 ℓ = 720 cm
3 Height increase per minute for Tank F
= 7200 ÷ 800
= 9 cm/min
Base area of Tank G
= 30 x 24
= 720 cm
2 Height decrease per minute for Tank G
= 720 ÷ 720
= 1 cm/min
Let t be the time taken for both the water levels to become the same.
9 t = 10 - 1 t
10 t = 10
1 t = 1 min
(b)
Height of the water level
= 9 t
= 9 x 1
= 9 cm
Answer(s): (a) 1 min; (b) 9 cm