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If the radius of a circle is decreased by  50% , find the percentage decrease in its area.


Options:
A .  72%
B .  74%
C .  75%
D .  76%
Answer: Option C

Let original radius  = R,       New radius =  `50/100  R =   R/2`

Original area = `pi R^2` and New area = `pi (R/2)^2`    =  ` (pi R^2)/(4)`

`:.` decrease in area  = `((3 pi R^2)/(4) xx (1)/(pi R^2) xx 100)`% = 75%



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