Math Is Fun Forum

Melllyy

Guest

Circles

What percentage of the circle is shaded. (the shape is a square drawn inside a circle)
The diameter of the circle is 2.8cm and one side of the square is 1.9cm

Please show workings =]

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: Circles

Im not sure what your asking?

Theres a square inscribed inside a circle. Are you saying the square is shaded and you want to know what percentage is shaded?

Last edited by LuisRodg (2008-03-12 01:56:30)

Melllyy

Guest

Re: Circles

omg sorry completely forgot about that important part

so yer its a square inside a circle. and all but the square in the circle is shaded.. hope that makes sense

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: Circles

Ok so everything but the square is shaded. So it would be something like this:

Ok so what you need to do is find the area of the whole circle which is:

A = PI * radius^2 = 6.1544 cm^2

And then you find the area of the square which is:

A = l * w = 3.61 cm^2

So the area of the part that is shaded is equal to the area of the whole circle minus the area of the square inside (which is not shaded) so:

6.15 - 3.61 = 2.54 cm^2

So 2.54 is the area of the section that is shaded. To find the ratio (percentage) of the section that is shaded in respect to the circle, it would be:

2.54/6.15 = 0.413 = 41.3%

Hope that helps.

Last edited by LuisRodg (2008-03-12 02:05:26)