Question:
A river 1.5 m deep and 36 m wide is flowing at the rate of 3.5 km/hr. Find the amount of water (in cubic metres) that runs into the sea per minute.
Solution:
We have,
Depth of the river, $h=1.5 \mathrm{~m}$,
Width of the river, $b=36 \mathrm{~m}$,
Speed of the flowing water, $l=3.5 \mathrm{~km} / \mathrm{hr}=\frac{3.5 \times 1000 \mathrm{~m}}{60 \mathrm{~min}}=\frac{175}{3} \mathrm{~m} / \mathrm{min}$
Now,
The amount of water that runs into the sea per minute $=l b h$
$=\frac{175}{3} \times 36 \times 1.5$
$=3150 \mathrm{~m}^{3} / \mathrm{min}$
So, the amount of water that runs into the sea per minute is 3150 m3.