Maths-
General
Easy

Question

The diameter of the three circles in this figure are 21 cm, 14 cm and 7 cm. What is the area of the shaded  region?

hintHint:

To find the area of shaded region subtract the area of circles inside from the outer circle.

The correct answer is: 154 cm2


    The diameters of three circle in the figure is given.
    Diameter of outer circle = 21 cm
    rightwards double arrow Radius  = fraction numerator text  diameter  end text over denominator 2 end fraction
    21 over 2 cm
    Area of the outer circle = straight pi r2
    22 over 7 × (21 over 2)2
    = 346.5 cm2
    Diameter of the larger circle inside = 14 cm
    rightwards double arrow Radius  = fraction numerator text  diameter  end text over denominator 2 end fraction
    14 over 2 =  7 cm
    Area of the larger circle inside = straight pi r2
    22 over 7 × 72
    =  154 cm2
    Diameter of the smaller circle inside = 7 cm
    rightwards double arrow Radius  =  fraction numerator text  diameter  end text over denominator 2 end fraction
    7 over 2  cm
    Area of the smaller circle inside = straight pi r2
    equals 22 over 7 × (7 over 2)2
    = 38.5 cm2
    Area of the shaded region = Area of the outer circle - Area of the larger circle inside - Area of the smaller circle
    = 346.5 cm2 - 154 cm2 - 38.5 cm2
    = 154 cm2

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