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In one fortnight of a given month, there...

In one fortnight of a given month, there was a rainfall of 10cm in a river valley. If the area of the valley is 7280` km^2`. show that the total rainfall was approximately equivalent to the addition to the normal water of three rivers each 1072 km long, 75 m wide and 3 m deep.

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Volume of rainfall in the valley in one fortnight
=Area of valley`xx`height of rainfall
=7280 `km^(2)xx10` cm
=7280 `m^(2)xx(10)/(10^(5))`km=0.728 `km^(3)`
volume of water in 1 river =1072 km `xx` 75m`xx` 3x
volume of water in 3 such rivers =`xx` 1072 km `xx(75)/(10^(3))"km"xx(3)/(10^(3))`km
=0.724 `km^(3)`1
From equations(1) and (2) we see that both volumes are approximtely equal.
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