Question

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

Answer 1

Given, a river $3m$ deep and $40m$ wide is flowing at the rate of $2km$ per hour.

Area of cross section of the river $=3\times 40=120m^2$

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

$=120m^2$ $\times$ $2$ $\frac{km}{hr}$

$=120m^2$ $\times$$\left(2000/60\right)$ $\frac{m}{min}$

$=2$ $\times$ $2000$ $\frac{m^3}{min}$

$=4000m^3$

Since$1m^3$ $=1000$ litres

So, $4000m^3$ $=4000$ $\times$ $1000$ litres $=4000000$ litres

So, in $1$ minute, the amount of water that will fall into the sea is $4000000$ litres.