Question

A rectangular water tank is 80m*40m water flows into it through a pipe 40 cm sq. At the opening at a speed of 10km/hr. By how much the water level will rise in the tank in half an hour?

Answer 1

Let the water, h mtr. will rise in the tank

l×b×h=Area×speed×time

80×40×h=40/100×100×10000×1/2

h=11/60m=100/160cm=5/8cm

Answer 2

The water level will change by 6.25 mm.

Step-by-step explanation:

Let the water level in the tank will rise by h meters after 30 minutes.

So, the volume of water flows into the tank is (80 × 40 × h) = 3200h cubic meters.

Now, water is flowing at the speed of 10 km/hr i.e. $\frac{10 \times 1000}{60} = 166.67$ meters/hr.

through a pipe of cross-section area 40 square cm i.e. $\frac{40}{10000} = 0.004$ square meters.

So, the total volume of water flow into the tank in 30 minutes is (166.67 × 0.004 × 30) = 20 cubic meters.

Hence, 3200h = 20

⇒ h = 0.00625 meters = 6.25 mm. (Answer)