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.