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...

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- Jun 23rd 2009, 12:54 PMadeshSBFind 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... - Jun 23rd 2009, 01:16 PMmasters
Hi adeshSB,

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

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

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

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

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