A river 1.5 m deep and 36 m wide is flowing at the rate of 3.5 km/hr.

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.