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A circular disc has a radius of 10cm. Find the percentage increase in its area if the...

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karengervasi | Student | (Level 3) eNoter

Posted July 4, 2013 at 5:10 AM via iOS

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A circular disc has a radius of 10cm. Find the percentage increase in its area if the radius is increased by 2%

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted July 4, 2013 at 5:16 AM (Answer #1)

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The area of a circle with radius r is equal to `A = pi*r^2` .

Initially the circular disc had a radius of 10 cm. Its area was `pi*10^2 = 100*pi`

When the radius is increased by 2%, the area is `pi*(10*1.02)^2` = `104.04*pi` .

The percentage increase in area is `((104.04*pi - 100*pi)*100)/(100*pi)` = 4.04

The increase in the area is 4.04%

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