Question

A river 3m deep and 40m wide is flowing at the rate of 2km per hour. How much water will fall into the sea in a minute?

Answer 1

Hint: In this question use the given dimensions of the river to calculate area of the river, using the area of the river calculate the volume by multiplying area and the rate flow of water.

Complete step-by-step answer:
Given data

A river is 3 meter deep and 40 m wide is flowing at the rate of 2 km/hr.

Rate (r) of flow = 2 km/hr.

Now as we know 1 km =1000 meter and 1hr = 60 minute.

Therefore Rate (r) of flow = (2000/60) m/min.

So the area (A) of the cross section of the river = depth of river multiplied by width of river

$ \Rightarrow A = 3 \times 40 = 120{\text{ }}{{\text{m}}^2}$

Now the volume (V) of the water flowing through this cross section in every minute = area

multiplied by rate of flowing.

$ \Rightarrow V = A \times r$

$ \Rightarrow V = 120 \times \dfrac{{2000}}{{60}} = 4000$ $m^3$/min.

Now as we know 1$m^3$ = 1000 liters.

Therefore 4000 $m^3$ = 4000000 liters.

So in 1 minute, water will fall into the sea 4000000 liters.

So this is the required answer.

Note: Although it was asked to convert ${m^3}$ into liters, it is advised to have knowledge about these basic conversions according to Indian conversion system. 1$m^3$ = 1000 liters. There are more units for water measurement just like cubic feet per second (cfs ) or acre foot (af).