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Question:

In a rain-water harvesting system, the rain-water from a roof of 22 m x 20 m drains into a cylindrical tank having diameter of base 2 m and height 3.5 m. If the tank is full, find the rainfall in cm. Write your views on conservation.

Solution:

Rectangular roof :l=22m,b=20m
Cylindrical tank :r=1m,h=3.5m
The volume of tank=πr²h=22/7×1×1×3.5=22/7×35/10=11m³
Area of roof=l×b=22×20=440m²
Rainfall=Volume of tank/Area of roof
∴Rainfall=11m³/440m²=0.025m
∴Rainfall is 2.5cm