A river 1.5 m deep and 30 m wide is flowing at the rate of 3 km per hour.

(b) 2250 m3

Length of the river = 1.5 m
Breadth of the river = 30 m
Depth of the river = 3 km = 3000 m

Now, volume of water that runs into the sea $=1.5 \times 30 \times 3000 \mathrm{~m}^{3}$

$=135000 \mathrm{~m}^{3}$

$\therefore$ Volume of water that runs into the sea per minute $=\frac{135000}{60}=2250 \mathrm{~m}^{3}$