The figure shows 2 tanks, Tank L and Tank M. Tank M is completely empty while Tank L is filled with water to the brim. Water from Tap K flows in at a rate of 3.6 litres per minute while water drains from Tap J at a rate of 1.44 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 L
= 40 x 20
= 800 cm
2 1 ℓ = 1000 cm
3 3.6 ℓ = 3600 cm
3 1.44 ℓ = 1440 cm
3 Height increase per minute for Tank L
= 3600 ÷ 800
= 4.5 cm/min
Base area of Tank M
= 20 x 24
= 480 cm
2 Height decrease per minute for Tank M
= 1440 ÷ 480
= 3 cm/min
Let t be the time taken for both the water levels to become the same.
4.5 t = 12 - 3 t
7.5 t = 12
1 t = 1.6 min
(b)
Height of the water level
= 4.5 t
= 4.5 x 1.6
= 7.2 cm
Answer(s): (a) 1.6 min; (b) 7.2 cm