Question

a river 3m deep and 40m wide is flowing at the rate of 2km per hour how
much water will fall in to the see in a minute

Answer 1

Area of cross section of the river = 3 * 40 = 120 m2

Now, volume of water flowing through this cross section in every minute = Area * rate

                                                                                                 = 120 * 2 km/hr

                                                                                                 = 120 * (2000/60) m/min

                                                                                                 = 2 * 2000

                                                                                                 = 4000 m3

Since 1 m3 = 1000 litres

So, 4000 m3 = 4000 * 1000 litres = 4000000 litres

So, in 1 minute, water will fall into the sea is 4000000 litres

Answer 2

Area of cross section of the river = 3 × 40 = 120 m2.
Rate of water flow = 2km/h = (2000/60) m/min
Volume of water flowing through this cross-section in every minute = Area × Rate
= (120)×(2000/60) = 4000 m3 = 4000×106 cc = 40,00,000 Litres