Thread: Find the ratio of the white to the shaded area..?
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Old June 23rd, 2009, 03:16 PM
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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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