Question
Mon February 11, 2013 By:

In one fortnight there was a ainfall of 10cm in a river valley. If the area of the valley is 97280km^2, prove that total rainfall was approximately equivalent to the addition to the normal water of three rivers each 1072km long 75m wide and 3m deep.

Expert Reply
Tue February 12, 2013
There is some error in this question. The reason is given below.
 
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
 
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 ? 9.828 km3.
This shows that the amount of rain fall is not equal to the amount of water in three rivers.
 
Thus, there is some error in this question.
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