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Math Help - Find the ratio of the white to the shaded area..?

  1. #1
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    Find the ratio of the white to the shaded area..?

    Ok well...
    The diagram shows 2 concentric circles. The large one has a radius of 5cm and the smaller one has a radius of 3cm.

    Find the ratio of the white to the shaded area..?

    Can anyone help? Pleasee...
    Attached Thumbnails Attached Thumbnails Find the ratio of the white to the shaded area..?-pie.jpg  
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  2. #2
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    Quote Originally Posted by adeshSB View Post
    Ok well...
    The diagram shows 2 concentric circles. The large one has a radius of 5cm and the smaller one has a radius of 3cm.

    Find the ratio of the white to the shaded area..?

    Can anyone help? Pleasee...
    Hi adeshSB,

    The area of the shaded area is 9 \pi using A=\pi r^2

    The area of the bigger circle is 25 \pi using the same reasoning.

    The difference between these areas is the area of the white part which would be 25 \pi - 9 \pi = 16 \pi

    The ratio of the white to the shaded area would then be:

    \frac{16 \pi}{9 \pi}=\frac{16}{9}
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