Q27 of 35 Page 311

If the length of radius of a circular field was increased by 10%, let us write by calculating what per cent it increase the area of circular field.

Let the radius of the circular field be r units.


The area of a circle = πr2


Now, increasing the radius to 10%



New radius =1.1r


Area of new circle = π(1.1r)2


⇒ Area of new circle = 1.21πr2


Increase in area =1.21πr2 - πr2 =0.21πr2


Per centage increase in the area of circular field


⇒ Percentage increase = 21%


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