Q2 of 18 Page 176

Calculate the area of the shaded part of this picture.

Inner radius = r = 2 cm


Outer radius = R = 4 cm


Area of shaded part = Area of larger sector –Area of smaller sector


If x° is the angle at subtended at the sector,


Area of sector = r2


Here, x = 120°


Area of larger sector = 42× π =


Area of smaller sector = 22× π =


Area of shaded part = Area of larger sector –Area of smaller sector


= –


cm2


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2

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i) In the same circle, what is the length of an arc of central angle 75°?


ii) In a circle of radius one and a half times the radius of this circle, what is the length of an arc of central angle 75°?

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i) What should be the central angle of the piece to be cut out?


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What is the area of this figure?