500 persons are taking a dip into a cuboidal pond which is 80 m long and 50 m broad. What is the rise of water level in the pond, if the average displacement of the water by a person is 0.04m3 ?

Let the rise of water level in the pond be h meters, when 500 persons are taking a dip into a cuboidal pond.


Given that,



Average displacement by a person = 0.04 m3


Average displacement by 500 persons = 500 ×0.04 = 20 m3


So, the volume of water raised in pond is 20 m3


Also,


Length of pond, l = 80 m


Breadth of pond , b = 50 m


Height is h


And we know,


Where, l, b and h are the length, breadth and height of tank respectively


Volume of water raised in pond = 80(50)(h)


20 m3 = 4000h


h = 0.005 m = 0.5 cm


[As 1 m = 100 cm]


So, Raise in water height is 0.5 cm.


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