Question

a river 3m deep and 40m wide is following at the rate of 2km/hr. how much water will fall into the sea in a minute

Answer 1

Answer.....

• Water flowing in 1hour =(2kilometers)

• Water flowing in 2hour=(2000metres)

• Water flowing in 60minutes=(2000metres)

• Water flowing in 1minute=(2000/60metres=(100/3)=meters.

• It is in the shape of the cuboid.

• L=(length)
• B=(breath)
• H=(height)

• M=(metres)

• Length =100/3metres.
• Breath=40/3metres.
• Height =3metres

Therefore or hence

Water falling =(1minute)

=

$l \times b \times h$

=

$100 \div 3 \times 40 \times 3m {}^{2}$

=

$100 \times 40 \times 1m {}^{2}$

$4000m { }^{2}$

Answer 2

The amount of water that flows in 1 hr is product of it's breadth, width and speed in place of length.

• Volume of channel = l × b × h

•Volume of water flowing per hr = speed × b × h ______________________________

→ Volume of water = 3 m × 40 m × 2 km/h

→ Volume of water = 3m × 40 m × 2000 m/h

→ Volume of water = 24 × 10⁴ m³/h

______________________________

Thus volume of water is 1 hr

= 24 × 10⁴ m³

This means that volume of water flowing in each minute will be less.

______________________________

Hence by unitary method,

Volume of water in 1 minute

= 24/60 × 10⁴ m³

= 4000 m³

Answer : 4000 m³