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प्रश्न
In one fortnight of a given month, there was a rainfall of 10 cm in a river valley. If the area of the valley is 7280 km2, 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.
उत्तर
Area of the valley = 7280 km2
If there was a rainfall of 10 cm in the valley then amount of rainfall in the valley = Area of the valley × 10 cm
Amount of rainfall in the valley = 7280 km2 × 10 cm
`=7280×(1000m)^2×10/100m`
`=7280×10^5m^3`
`=7.28×10^8m3`
Length of each river, l = 1072 km = 1072 × 1000 m = 1072000 m
Breadth of each river, b = 75 m
Depth of each river, h = 3 m
Volume of each river = l × b × h
= 1072000 × 75 × 3 m3
= 2.412 × 108 m3
Volume of three such rivers = 3 × Volume of each river
= 3 × 2.412 × 108 m3
= 7.236 × 108 m3
Thus, the total rainfall is approximately same as the volume of the three river
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