Question

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 97280 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.

Answer 1

Area of the valley, A = 97280 km²

Level in the rise of water in the valley, h = 10 cm = (10/100000) km = (1/10000) km

Thus, amount of rain fall = Ah = 97280 km² × (1/10000) km = 9.828 km³

in 14 days 9.828km3 in 1 day 0.702km3

Volume of water in each river = length × breadth × height = 1072 km × 75 m × 3 m = 1072 km × (75/1000) km × (3/1000) km = 0.2412 km³

Thus, the volume of water in three rivers = 3 × 0.2412 km³ = 0.7236 km³ 

and amt of rainfall= 0.702 km3 which is approximately equal 

This shows that the amount of rain fall is approximately equal to the amount of water in three rivers.