The figure shows 2 tanks, Tank R and Tank S. Tank S is completely empty while Tank R is filled with water to the brim. Water from Tap Q flows in at a rate of 1.2 litres per minute while water drains from Tap P at a rate of 2.16 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 R
= 40 x 20
= 800 cm
2 1 ℓ = 1000 cm
3 1.2 ℓ = 1200 cm
3 2.16 ℓ = 2160 cm
3 Height increase per minute for Tank R
= 1200 ÷ 800
= 1.5 cm/min
Base area of Tank S
= 20 x 24
= 480 cm
2 Height decrease per minute for Tank S
= 2160 ÷ 480
= 4.5 cm/min
Let t be the time taken for both the water levels to become the same.
1.5 t = 12 - 4.5 t
6 t = 12
1 t = 2 min
(b)
Height of the water level
= 1.5 t
= 1.5 x 2
= 3 cm
Answer(s): (a) 2 min; (b) 3 cm